Zelenskiy, who gained billions of dollars' worth of U.S. weaponry and moral support from the Biden administration, is facing a sharply different attitude from Trump. The Republican president has said he wants to quickly wind down the three-year war, improve relations with Moscow and recoup U.S. money spent to support Ukraine.

Trump has also adopted a much less committed stance toward European security, to which the U.S. has been an indispensable partner since World War Two.

The change in tone from the United States, Ukraine's most important backer, has sent shockwaves across Europe and stoked fears that Kyiv could be forced into a peace deal that favors Russia.

The minerals agreement negotiated in recent days would open up Ukraine's vast mineral wealth to the United States but does not include American security guarantees, a disappointment for Ukraine.

It gives Washington the right to recoup some of the billions of dollars in costs of the U.S. weaponry supplied to Kyiv through a reconstruction investment fund tied to the sale of Ukraine's rare earth minerals.

A Center for Strategic and International Studies report last year found that about two-thirds of the money Congress appropriated for Ukraine was spent in the United States.

Ukraine hopes the agreement will spur Trump to support Kyiv's efforts to recapture territory seized by Russia. The deal also could win support from Republicans in Congress for a new round of aid to the war-torn country.

Trump has engaged in a long-distance feud with Zelenskiy in recent weeks, criticizing his handling of the war, calling him a dictator and urging him to agree to the minerals deal.

But during a joint news conference with visiting British Prime Minister Keir Starmer on Thursday, Trump said: "Did I say that? I can't believe I said that."

Trump also noted he was looking forward to meeting Zelenskiy and praised the Ukrainian military for its bravery.

"We're working very hard to get that war brought to an end. I think we've made a lot of progress, and I think it's moving along pretty rapidly," Trump said.

"It'll either be fairly soon or it won't be at all," he added, without elaboration.

Starmer said he and Trump had discussed a plan to reach a peace that is "tough and fair, that Ukraine will help shape, that is backed by strength to stop Putin coming back for more."

Starmer said Britain was prepared to contribute military personnel on the ground to serve as peacekeepers "because that is the only way that peace will last." Trump dodged a plea from Starmer for U.S. participation.

Under the agreement Trump and Zelenskiy are expected to sign on Friday, Ukraine would contribute 50% of "all revenues earned from the future monetization of all relevant Ukrainian Government-owned natural resource assets" to a reconstruction fund jointly owned and managed by the United States and Ukraine.

The agreement does not name the assets in question, but says they would include deposits of minerals, oil, natural gas and other extractable materials as well as other infrastructure such as LNG terminals and ports.