SIR Keir Starmer tonight insisted he trusted Donald Trump but warned him Russia would never stop without America protecting Europe.

On his way to Washington for the White House summit with the President, the Prime Minister reckoned there were no issues between them.

But Sir Keir believes a peacekeeping force in Ukraine would not be credible without the US underwriting its protection — either from the air or with other protections.

He said: “The security guarantee has to be sufficient to deter Putin from coming again because my concern is if there is a ceasefire without a backstop, it will simply give him the opportunity to wait and to come again because his ambition in relation to Ukraine is pretty obvious, I think, for all to see.”

But Mr Trump repeated his demand that Europe should police any peace deal between Russia and a war-weary Ukraine.

After the Kremlin hit out at Britain and France for offering peacekeeping forces, Sir Keir snapped back: “Well I’m not answering to Putin.”

But he side-stepped questions on how the plan would work.

The Prime Minister told reporters on board his flight to Washington DC: “I’m considering how we preserve peace in Europe and how we get a lasting peace in Ukraine.

“I’m absolutely convinced that we need a lasting peace, not a ceasefire, and for that to happen we need security ­guarantees. Precisely what that layers up to, what that looks like, is obviously a subject of intense discussion.

“We will play our part and I’ve been clear we will need a US backstop of some sort.

But Mr Trump declared: “I’m not going to make security guarantees beyond very much.

“We’re gonna have Europe do that — Europe is their next-door neighbour.”

Following his make-or-break meeting with the President today, Sir Keir hosts European leaders in the UK on Sunday.

Ukraine President Volodymyr Zelensky confirmed last night he would attend after his own meeting with Mr Trump on Friday.

His country signalled it would sign a new accord with America for access to critical minerals — which Mr Trump has demanded as a price for further protection.

After two weeks of attacks from the US on Mr Zelensky, whom Mr Trump has branded a dictator and blamed for the 2022 Russian invasion, the PM played down the divisions.

He said: “There’s one aggressor here and that’s Russia.

“Russia can end this conflict tomorrow by withdrawing and stopping their aggression. All the discussion that follows, about talks, security guarantees, has to be seen in that context. They are the aggressor.

“They have invaded and occupied a sovereign country in Europe, and they bear full responsibility for the conflict.”

Asked if Mr Trump also believed that, Sir Keir said: “Of course, the President has been very clear about the peace that he wants. He’s right about that.

“We all want peace. The question is, how do we make sure it’s a lasting peace. There’s no issue between us on this.”

After Mr Trump’s relentless praise for Putin and trashing of Ukraine, the PM insisted America is still on our side. He said: “The President is clearly committed to Nato, committed to the special relationship.

“I’ve been absolutely resolute that we’re not going to choose between one side of the Atlantic and the other. We will work with the US, we will work with our European allies, that’s what we’ve done for decades and it’s what we’ll do whilst I’m Prime Minister.”

At a Cabinet meeting last night, Mr Trump said the minerals deal with Ukraine would be a “very big agreement”.

The $500billion deal is seen as a way for Ukraine to get the US back onside. Mr Trump said: “The deal we’re making brings us great wealth.

“We get back the money we spent, and we hope we’re going to be able to settle this up.”

And he insisted it would benefit Ukraine, too, adding: “Nobody’s going to be messing around with people.”