U.S. President Donald Trump said on Thursday that a minerals deal with Ukraine is the security guarantee Kyiv needs against Russia, brushing aside a plea from British Prime Minister Keir Starmer for a commitment of U.S. military support.

Starmer, who was meeting Trump at the White House for the first time since the U.S. leader took office, turned on the charm, saying peace in Ukraine had only become possible because of Trump.

However, underlying differences between the allies remained, including transatlantic frictions over U.S.-Russia talks aimed at ending the Russia-Ukraine conflict and Trump's tariff threats.

Before the meeting, Starmer had said there could be no long-term peace in Ukraine without firm U.S. security guarantees – an argument Trump all but dismissed.

"We are a backstop because we'll be over there, we'll be working," Trump said, referring to the economic partnership. "We're going to have a lot of people over there."

Asked whether he could trust Russian President Vladimir Putin, Trump said, "Trust and verify," echoing former U.S. President Ronald Reagan's views on negotiations with the Soviet Union.

Noting that talks towards ending the Russia-Ukraine conflict were moving briskly, Trump said, "It will either be fairly soon, or it won't be at all." Starmer said not just any deal would do, underscoring the concern among European nations that a rushed peace deal with Russia might lead to further instability in Europe.

"We have to get it right," Starmer said at a joint press conference with Trump. "It can't be peace that rewards the aggressor."

Starmer is the latest European leader to meet Trump, after French President Emmanuel Macron came to the White House on Monday for a friendly encounter that also displayed stark differences over the Russia-Ukraine conflict.

Starmer has signaled that Britain will increase defense spending and has tried to reassure the U.S. president that Europe will provide support and security guarantees to Kyiv if peace talks with Russia are successful.

On Thursday, Trump reaffirmed the United States' long-standing commitment to the mutual defense of NATO nations, even if European peacekeepers end up in Ukraine. "I support it. I don't think we're going to have any reason for it," he said.

Starmer has said he is open to British troops providing security guarantees to Ukraine but only alongside other European nations and with "the right conditions in place."

The two leaders also negotiated a bilateral trade agreement. A wide-ranging free trade deal has eluded the countries since Trump's 2017-2021 term in office, but the U.S. president said the two countries could reach a deal "very shortly."

Asked by a reporter whether Starmer had convinced him to abandon threats to impose tariffs on Britain, Trump said, "He tried. He was working hard, I'll tell you that."

"We could very well end up with a real trade deal where the tariffs wouldn't be necessary," Trump said. "We'll see."

(With input from Reuters)