He was speaking after attending a gathering of European leaders at Blenheim Palace in Oxfordshire, where Sir Keir Starmer urged them to stand firm in their support of Ukraine.

It comes as Donald Trump prepares to address Republicans at their national convention in Milwaukee, with the fear in Europe that if he wins November's presidential election he'll be less committed to the security of the continent than President Biden.

More on the battle for the White House in a moment, but first, Chris Mason, our political editor, is here.

Chris.

Yes, evening to you, Clive.

The meeting today in Oxfordshire was that of the European political community.

It's a new collection of around about 40 European countries, and it came together specifically to respond to the war in Ukraine, and President Zelensky was there.

This evening I have been talking to him, I've been talking to him about the reality of being a wartime leader, dealing with, as he is, his fourth UK Prime Minister in just two years, and then, crucially, the politics of the United States.

Take a look.

When Donald Trump said last year that he thought this war could end within 24 hours if he was to meet both you and Vladimir Putin, what did you make of that?

So everybody will be happy if one person in the world doesn't depend, Donald Trump or not.

Okay, Donald Trump.

If one person in the world, and this person Donald Trump, can stop the war during 24 hours.

The question is, what's the price, and who will pay?

So I think in his, I don't, no, no, I'm not meaning that his idea to push us to pay, but if he wants to do it during 24 hours, the simple way is to push us to pay.

Because it's understandable how.

It means just stop and give.

And forget.

Sanctions out, everything out, Putin will take the land, Putin will be, will make a victory for his society.

We will never go on this, never.

And there is no any guy in the world who can push us to do it.

Donald Trump this week has picked the man he would like to be his vice president, J.D.

Vance, who has said in the past that he doesn't really care what happens in Ukraine one way or another.

What do you make of those remarks?

Maybe he really doesn't understand what goes on in Ukraine.

So for us, we have to work with the United States.

And if new team will come, we have to work with them.

We need their support.

Could be hard work, I guess.

Hard work.

Could be hard work to persuade them.

Yes, but we don't, I mean, we don't afraid of hard work.

Did your heart sink last week when President Biden, standing right next to you, introduced you as President Putin of all people?

No, he just made a mistake.

Honestly, for me, it means nothing.

President Zelensky will meet Kirstarma and his senior ministers tomorrow.

He told me he wants a special relationship with Sakhir and permission to fire Western weapons deep into Russia.

We need very strong support from Prime Minister.

We need this decision about long distance weapon, long range to use it.

We need it very much.

They targeting our hospitals, schools, universities, like I said to you, they targeting our just civilians.

We just want to answer to the exactly to the point where from there they target us.

How does this war end and how soon could it do?

Do you have to restore Ukraine to the borders that you had before 2014 in order for you to be convinced that that is grounds for peace?

It will depend on partners who will put pressure on Russia so that Russia agrees to sit down and think about ending the war.

It doesn't mean that all the territories are won back by force.

I think that the power of diplomacy can help.

I want to try and understand on behalf of our audience how it is to be a wartime leader.

How do you keep going?

I'm not sure that I'm some special man or something like this, really.

I had, I think, very good parents and to have, I think, values, values of ordinary, normal people.

We all have our limits, we're all human.

Could you reach the point where you couldn't go on as president?

Yes, I think yes, everybody.

Because we're just people.

You could reach the point where you'd have to hand over to someone else?

Yes, of course.

In the next year, the next few years or?

After the war.

So you keep going until the war is over?

Yes, we'll finish with it.

We have to finish with it and we have to finish with him.

I think it's very important for our people, our country.

Finish with Vladimir Putin?

Yes.

Mr. President, thank you for your time.

Thanks so much.

Thank you.

It's a fascinating interview, Chris, but one wonders, given America's centrality to NATO and European security in general, whether this gathering at Blenheim Palace was nothing more than just a talking shop?

The curiosity, Clive, of this structure, this new political structure, that you'd be forgiven for not having heard of, is that they try to make a virtue of it being informal and something of a talking shop.

There isn't what's known as a communique afterwards.

What was striking today was that Jens Stoltenberg, the NATO Secretary General, was there and I spoke to him and asked him that exact question.

And he was trying to make an argument that he was trying to play a role that bridged the Atlantic, European members of NATO and others, and the United States.

Conscious as he is, he's about to stand down from that role, of the potential for turbulence in US politics and where that leaves NATO.

He did make the point, though, that he was NATO Secretary General during Donald Trump's term in the White House and yes, there was rhetoric from President Trump, but he said they stepped up when they needed to.