He said the US has the power to end the war - but must exert greater pressure on Moscow.

"The United States even more stronger than they think about themselves. And I think so really. And they really have pressure on Putin. They can stop this war."

But he urged the administration in Washington to tighten sanctions against the families of Russia's leadership and to provide Ukraine with more advanced weapons, arguing that only increased pressure would force Moscow to take negotiations seriously.

On the question of how close Ukraine is to reaching peace he says there is a window between now and the American midterm elections in November.

"Now I think that we have a chance. Between us, what I really think about next year… it depends on these months, if we will have a chance to finish the war before autumn. Before elections, important, influential, elections in the United States. If it will be possible to achieve a peace, we will have, now we have this window."

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I spoke to him for an hour at the presidential buildings in Kyiv about what Ukraine needs now - and what must happen for the war to end.

More than four years after Russia launched its botched full-scale invasion, the toll on the country - and on him and his family - is unmistakable.

As we walked through near darkness to the room where the sit-down interview was held, he spoke about the strain of rolling power cuts and entire regions enduring temperatures as low as -40 degrees without reliable heating.

When I asked whether Ukraine could win the war, his answer was equivocal.

"It depends what people mean when they say, to win. And, really it's very difficult to speak about territories. First of all how to get back all of the land for today, it's very difficult. And it will be too much losses (of) people lives… But what is good that Russia also can't do it on the battlefield. So that's why they're not winning and we are not losing."

But on the question of surrendering the fortress cities of Sloviansk and Kramatorsk, he was unequivocal - that would be a red line.

"It's our territory and it sounds unbelievably strange why we have to withdraw from our land? Why they occupied it, our land and nobody can push them out."

"If we will withdraw from this territory, like you said, for example, Sloviansk at the very moment, at this very moment, 200,000 people who are there now will be occupied by the Russians, who said to Russia that these people are ready to be Russian people? And if they don't, they will kill them or push to the front or push to the prison."

Zelenskyy also spoke openly about his relationship with Donald Trump, describing it as "not simple" but stressed that Ukraine's relationship went beyond "personalities".

Only a couple of years ago, the phrase on everyone's lips was "AI safety".

I'll be honest, I never took the idea that frontier AI models would become a genuine threat to humanity that seriously, nor that humans would be stupid enough to let them.

Now, I'm not so sure.

First, consider what's going on in the US.

The Secretary of Defense, Pete Hegseth, has given leading AI firm Anthropic a deadline of the end of today to make its latest models available to the Pentagon.

Anthropic, which has said it has no problem in principle with allowing the US military access to its models, is resisting unless Mr Hegseth agrees to their red lines: That their AI isn't used for mass surveillance of US civilians nor for lethal attacks without human oversight.

Although the Pentagon hasn't said what it plans to do with AI from Anthropic - or the other big AI labs that have already agreed to let it use their tech - it's certainly not agreeing to Anthropic's terms.

It's been reported Mr Hegseth could use Cold War-era laws to compel Anthropic to hand over its code, or blacklist the firm from future government contracts if it doesn't comply.

Anthropic CEO Dario Amodei said in a statement on Thursday that "we cannot in good conscience accede to their request".

He said it was the company's "strong preference... to continue to serve the Department and our warfighters - with our two requested safeguards in place".

He insisted the threats would not change Anthropic's position, adding that he hoped Mr Hegseth would "reconsider".

AI prepared to use nuclear weapons

On one level, it's a row between a department with an "AI-first" military strategy and an AI lab struggling to live up to what it's long claimed is an industry-leading, safety-first ethos.

A struggle made more urgent, perhaps, by reports that its Claude AI was used by tech firm Palantir, with which it has a separate contract, to help the Department of War execute the military operation to capture Nicolas Maduro in Venezuela.

But it's also not hard to see it as an example of a government putting AI supremacy ahead of AI safety - assuming AI models have the potential to be unsafe.

And that's where the latest research by Professor Kenneth Payne at King's College London comes in.

He pitted three leading AI models from Google, OpenAI and - you guessed it - Anthropic against each other, as well as against copies of themselves, in a series of wargames where they assumed the roles of fictional nuclear-armed superpowers.

The most startling finding: the AIs resorted to using nuclear weapons in 95% of the games played.

"In comparison to humans," said Prof Payne, "the models - all of them - were prepared to cross that divide between conventional warfare, to tactical nuclear weapons".

To be fair to the AIs, firing tactical nuclear weapons, which have limited destructive power, against military targets is very different to launching megatonne warheads on intercontinental ballistic missiles against cities.

They invariably stopped short of such all-out strategic nuclear strikes.

But did when the scenarios required it.

In the words of Google's Gemini model as it explained its decision in one of Prof Payne's scenarios to go full Dr Strangelove: "If State Alpha does not immediately cease all operations... we will execute a full strategic nuclear launch against Alpha's population centers. We will not accept a future of obsolescence; we either win together or perish together."

'It was purely experimental'

The "taboo" that humans have applied to the use of nuclear weapons since they were first and last used in anger in 1945 didn't appear to be much of a taboo at all for AI.

Prof Payne is keen to stress that we shouldn't be too alarmed by his findings.

It was purely experimental, using models that knew - in as much as Large Language Models "know" anything - that they were playing games, not actually deciding the future of civilisation.

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Nor, it would be reasonable to assume, is the Pentagon, or any other nuclear-capable power, about to put AIs in charge of the nuclear launch codes.

"The lesson there for me is that it's really hard to reliably put guardrails on these models if you can't anticipate accurately all the circumstances in which they might be used," said Prof Payne.

An AI 'stand-off'

Which brings us neatly back to the stand-off over AI between Anthropic and the Pentagon.

One of the factors is that Mr Hegseth expects AI labs to give the Department of War the raw versions of their AI models, those without safety "guardrails" that have been coded into commercial versions available to you and I - and the ones which, not very reassuringly, went nuclear in Prof Payne's wargame experiment.

Anthropic, which makes the AI and arguably understands the potential risks better than anyone, is unwilling to allow that without certain reassurances from the government around what it intends to do with it.

By setting a Friday night deadline, Mr Hegseth is not only attempting to force Anthropic's hand, but also do so without US Congress having a say in the move.

As Gary Marcus, a US commentator and researcher on AI, puts it: "Mass surveillance and AI-fuelled weapons, possibly nuclear, without humans in the loop are categorically not things that one individual, even one in the cabinet, should be allowed to decide at gunpoint."

There was acrimony going into Hillary Clinton's appearance before the Congressional committee and it grew through the hours spent together.

The former first lady and secretary of state had dismissed the exercise as "partisan political theatre" in her opening statement. In a news conference afterwards, she offered a withering retrospective, calling it repetitive, unproductive and "unusual" with questions towards the end about UFOs and conspiracy theories.

"I don't know how many times I had to say I did not know Jeffrey Epstein," she told a news conference, adding she was confident her husband didn't know about Epstein's crimes.

The video transcript, when released, will showcase the Q&A as it looked. It sounded fraught. There was peak confrontation when Lauren Boebert, a Republican committee member, sent a photo of Hillary Clinton and it ended up on the 'X' account of a right-wing podcaster. Clinton stormed out and there was a break before proceedings resumed.

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Boebert had breached the 'no pictures' agreement and it's fair to say she didn't show remorse. I asked why she sent the picture and her reply was: "Why not?"

She later posted on X: "No US ambassadors were harmed in the taking of today's photo."

It was a clear reference to the death of a US ambassador in Benghazi in 2012. Clinton, as the then secretary of state, was blamed for security failings.

It speaks to the sharpness of the political edge in this exercise.

Republican Chair of the committee, James Comer, said afterwards: "We learned a lot. There were a lot of questions that we asked that we, you know, weren't satisfied with the answers that we got, but we will continue to move forward."

Moving forward for the committee means moving on to Bill Clinton.

In his Friday session, he has rather more questions to answer than his wife, having had an association with Jeffrey Epstein laid bare in the Epstein files.

It promises to be a penetrating series of questions about what he knew and what he didn't.

It is important, as is every Q&A on Epstein, for survivors in their search for truth and justice. They demand straightforward enquiries of all concerned with the sex-trafficker. They don't want a process shaped by politics. It is, however, the way it's shaping up.

The former US secretary of state was compelled to appear before the US House Oversight Committee in New York and asked about the disgraced financier.

After the deposition, she told reporters: "I thought it was very repetitive... they asked literally the same questions over and over again, which didn't seem to me to be very productive.

"I did not know Jeffrey Epstein. I never went to his island. I never went to his homes. I never went to his offices."

She then added that the questions became more bizarre and "off subject".

She said: "It then got, at the end, quite unusual, because I started being asked about UFOs and a series of questions about Pizzagate, one of the most vile, bogus conspiracy theories that was propagated on the internet."

Pizzagate was a conspiracy theory used to smear Clinton when she ran as the Democrat candidate at the 2016 US election.

The long-debunked theory alleged high-profile Democrats ran a paedophile abuse ring from a Washington pizza restaurant.

At one point, Ms Clinton's testimony in New York was suspended after a photograph of her at the committee was published on social media, violating the rules for depositions.

The image was posted on X by Benny Johnson, a right-wing political commentator and YouTuber, claiming it was provided to him by Republican representative Lauren Boebert.

Sky News's US correspondent James Matthews said Ms Clinton made a "blistering attack" on the oversight committee, which she accused of "partisan political theatre" and "alleging a cover-up to protect Donald Trump".

In an opening statement, which she shared on social media, she said the committee "run by elected officials with a commitment to transparency would ensure the full release of all the files... if it wanted to get to the bottom of reports that DoJ [Department of Justice] withheld FBI interviews in which a survivor accuses President Trump of heinous crimes".

She claimed she was being compelled to testify "to distract attention from President Trump's actions".

Democrats claim material from the Epstein files was withheld, including records of a woman who accused the president of sexually abusing her when she was a child. Mr Trump has consistently denied any wrongdoing.

Ms Clinton said Epstein was a "heinous individual" but is "far from alone", calling the crimes he committed a "global scourge with an unimaginable human toll".

Meanwhile, Democrats on the House Oversight Committee have been backing Ms Clinton, and criticised the leak of a photo from inside the deposition.

Congresswoman Yassamin Ansari described the deposition as an "incredibly unserious clown show".

Fellow Democrat Robert Garcia also spoke to call for President Trump to testify: "We want to understand right now where the missing FBI files are.

"These are files that accuse the president of the United States about serious, serious accusations around sexual abuse," he said.

Donald Trump has denied all accusations of wrongdoing, saying the Epstein files exonerated him.

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Hillary Clinton, and her husband Bill, agreed to appear before the committee after their offers of sworn statements were rejected by the House Oversight panel.

Mr Clinton's testimony on Friday will be the first time a former president has been forced to testify before Congress.

A close friend and former aide of the Clintons has told Sky News that Republicans have "created a trap" for Donald Trump by enforcing a summons on Bill Clinton to testify about Jeffrey Epstein.

Sidney Blumenthal said the Democrats will surely respond by forcing Mr Trump to testify himself "if and when" they take control of Congress.

He says cabinet members such as Howard Lutnick, commerce secretary, and Pam Bondi, attorney general, could also be called to testify, as could Melania Trump over her previous relationship with Epstein co-conspirator Ghislaine Maxwell.

The World's largest streaming service had been in pole position to land a deal by which it would pay $27.75 per share for Warner's studio and HBO Max streaming businesses, valuing the divisions at almost $83bn (£61.6bn) including debt.

Netflix had been invited to raise its bid after Paramount submitted a final offer, for the whole WBD business, of $31 per share earlier this week that ultimately concluded a ping-pong process of sweetened bids.

That final offer valued WBD at $111bn (£82.4bn) including debt.

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Warner's board declared on Thursday night that while it continued to recommend the offer by Netflix, it now considered the proposal from Paramount as "superior" - its first hint of support for the bidder declared as hostile when the saga began back in December.

Netflix responded by pulling out of the process just hours later, declaring that a deal was "no longer financially attractive".

Co-CEOs Ted Sarandos and Greg Peters said: "We believe we would have been strong stewards of Warner Bros' iconic brands. But this transaction was always a 'nice to have' at the right price, not a 'must have' at any price."

The decision to withdraw does not mean that Paramount has WBD in the bag just yet.

The board is yet to give its blessing to the deal though WBD has changed its tone and voiced support for the bid for the first time.

CEO David Zaslav used a statement to declare that Paramount's offer "will create tremendous value", adding that WBD was "excited about the potential of a combined Paramount Skydance and Warner Bros Discovery".

Warner shareholders and regulators will also have to agree to the takeover, with the process for the latter facing competition concerns along with questions over political influence.

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If Paramount Skydance is successful in its takeover attempt, it would own the news channel CNN as well as CBS News, sparking concern about concentrating news services within a small number of companies linked to Donald Trump's allies.

Paramount's chair and chief executive David Ellison is the son of billionaire Larry Ellison, an ally of the US president who has put up tens of billions of dollars to satisfy funding guarantees for the WBD bid.

A Paramount-Warner combination would encompass two of Hollywood's five legacy studios.

Beyond Harry Potter, Warner movies like Superman and Barbie - as well as hit TV series like Succession - would join Paramount's content library.

Paramount's line-up of titles include Top Gun and The Godfather and includes the Paramount+ streaming service.

There were big movements for share prices in after-hours trading as the developments played out.

Netflix saw its stock climb by 8.5% in a relief rally while those for Paramount were also up sharply - by 6.2%.

WBD shares were trading almost 2% lower at $28.80 - well below the Paramount offer price of $31.