The negotiations illustrate the perilous diplomatic waters that Ukraine's leader must navigate as he seeks to win the backing of Donald Trump and secure post-war security guarantees, as the U.S. president pushes to end the war with Russia.

U.S. Treasury Secretary Scott Bessent presented a draft deal during a trip to Kyiv on Wednesday after Zelenskiy set out the contours of an agreement that could open up Ukraine's vast natural wealth to U.S. investment, two sources familiar with the matter said.

Ukraine, which is trying to forge ties with Trump by appealing to his penchant for a deal, has not disclosed the content of the discussions, though two Ukrainian sources said on Friday that Kyiv had given a revised draft to the U.S. side.

Asked by reporters what the problem with the U.S. document was, Zelenskiy said in his most candid comments to date: "it's not in our interest today, not in (the) interest of (a) sovereign Ukraine."

"There are not very concrete things about security guarantees in this document. That for me is very important: the connection between some kind of security guarantees and some kind of investment," he continued.

Zelenskiy's team has placed high importance on the need for Ukraine to receive guarantees from the U.S. that would deter Russia from launching a new invasion once a peace deal is reached.

Bessent has said the deal could provide Ukraine with a "security shield" and intertwine Kyiv's economy with the United States.

'VERY BOLD'

Two sources familiar with the matter told Reuters Zelenskiy had declined to sign the deal on Wednesday when the United States presented a document that proposed giving the United States ownership of half of Ukraine's critical minerals.

A third source described the U.S. ask of Ukraine as very bold, focusing on at least 50% of critical minerals and similar amounts of other resources, over a long period of time.

One of the sources said that the document contained no security guarantees. The first two sources said that Zelenskiy believed the document had been drawn up by the U.S. embassy in Kyiv.

Trump, who has not committed to continuing vital military aid to Ukraine, has said he wants $500 billion in rare earth minerals from Kyiv and that Washington's support needs to be "secured".

The minerals in question could include rare earth varieties, as well as titanium, uranium and lithium among others.

Talks between Zelenskiy and a U.S. delegation led by Vice-President JD Vance ended at the Munich Security Conference on Friday without an announcement of a deal.

Earlier that day, Zelenskiy had voiced concern about the U.S. proposal when he attended a 90-minute meeting with a bipartisan group of U.S. senators behind closed doors, three sources familiar with his presentation said.

He "felt he was being asked unreasonably to sign something he hadn't had a chance to read", one of them said on condition of anonymity. "I don't think he appreciated being given a take-it-or-leave-it thing."

Zelenskiy discussed his own proposal for a mineral deal with the United States, the source said, saying it was drafted to comply with the Ukrainian constitution.

Two sources characterized the proposal delivered by Bessent as "one-sided", but declined to elaborate.

Democratic Senator Brian Schatz, asked after the meeting if Zelenskiy considered the U.S. proposal one-sided, responded, "I think that's fair to say."

British Foreign Minister David Lammy, a close Kyiv ally, said on Saturday the best security guarantee for Ukraine against future Russian aggression was binding U.S. industry, business and defence capability into its future.

"That is what will make Putin sit up and pay attention, and that is what's attractive to a U.S. president who knows how to get a good deal," he said.