spoiler
The US will abandon trying to broker a Russia-Ukraine peace deal within days unless there are clear signs a truce can be reached, US Secretary of State Marco Rubio has warned.
"We're not going to continue with this endeavour for weeks and months on end," Rubio said, adding that the US had "other priorities to focus on".
Russia launched a full-scale invasion of Ukraine in 2022 and has placed a number of conditions on any potential ceasefire.
Despite the Trump administration's initial confidence that it could secure a deal quickly, attempts to reach a full ceasefire have yet to materialise, with Washington blaming both sides.
Following a meeting with European leaders in Paris about a potential ceasefire on Thursday, Rubio told reporters on Friday: "We need to determine very quickly now - and I'm talking about a matter of days - whether or not this is doable."
"If it's not going to happen, then we're just going to move on," he said about truce talks.
He said it was clear that a peace deal would be difficult to strike but there needed to be signs it could be done soon.
US President Donald Trump had said before he re-entered office that he would stop the fighting in the first 24 hours of his presidency.
Kremlin spokesman Dmitry Peskov, when asked to respond to Trump saying he expected an answer from Russia on a ceasefire, said "the negotiations taking place are quite difficult".
"The Russian side is striving to reach a peace settlement in this conflict, to ensure its own interests, and is open to dialogue," he said.
The comments come as Russian strikes on Ukraine continue. On Friday, Ukrainian President Volodymyr Zelensky said in a post on X that Russia had launched a volley of missile attacks that killed two people.
During a meeting with Italian Prime Minister Giorgia Meloni in Rome on Friday, US Vice President JD Vance said he was "optimistic" about ending the Ukraine war.
"I want to update the prime minister on some of the negotiations between Russia, Ukraine, and also some of the things that have happened even in the past 24 hours," he said.
"I won't prejudge them, but we do feel optimistic that we can hopefully bring this war - this very brutal war - to a close."
Rubio's warning follows separate news that Ukraine and the US took the first step towards striking a minerals deal, after an initial agreement was derailed when a February meeting between Trump and Zelensky erupted into a public shouting match.
On Thursday, the two countries signed a memorandum of intent stating that they intend to establish an investment fund for Ukraine's reconstruction as part of an economic partnership agreement.
The aim is to finalise the deal by 26 April, the memo published by the Ukrainian government says.
The details of any deal remain unclear. Previous leaks have suggested the agreement has been extended beyond minerals to control of Ukraine's energy infrastructure, as well as its oil and gas.
Ukrainian negotiators have tried to resist Trump's demands that a joint investment fund would pay back the US for previous military aid, but have seemingly accepted his claim that it would help the country recover after the war ends.
The memo said the "American people desire to invest alongside the Ukrainian people in a free, sovereign and secure Ukraine".
Zelensky had been hoping to use the deal to secure a US security guarantee in the event of a ceasefire deal, telling European leaders last month that "a ceasefire without security guarantees is dangerous for Ukraine".
The US has so far resisted providing Kyiv with security guarantees.
The White House argues the mere presence of US businesses would put off Russia from further aggression, but that did not exactly work when they invaded in 2022.
Economy Minister Yulia Svyrydenko announced the signing of the memorandum on X, with pictures of Svyrydenko and US Treasury Secretary Scott Bessent separately signing the document over an online call.
"There is a lot to do, but the current pace and significant progress give reason to expect that the document will be very beneficial for both countries," Svyrydenko wrote.
Bessent said the details were still being worked out but the deal is "substantially what we'd agreed on previously."
Trump hinted at the deal during a press conference with Italian leader Giorgia Meloni, saying "we have a minerals deal which I guess is going to be signed on (next) Thursday...And I assume they're going to live up to the deal. So we'll see. But we have a deal on that."
Ivanna Klympush-Tsintsadze, an MP and the chair of Ukraine's parliamentary committee on EU Integration, told the BBC the Ukrainian Parliament will have "the last word" in the deal.
She added: "I hope that there will be enough reasoning to ensure that whatever is signed, and if it is going to be ratified that it is in the interest of our country and our people.
The memo release comes as a 30-day moratorium on striking Ukrainian energy infrastructure ordered by Russian President Vladimir Putin expires.
Peskov said Putin had not yet issued any new orders regarding the temporary ceasefire.
On Thursday, Ukraine's Foreign Minister Andrii Sybiha met Rubio and Trump's special envoy Steve Witkoff in Paris to discuss how to end the war.
Sybiha said they had "discussed the paths to a fair and lasting peace, including full ceasefire, multinational contingent, and security guarantees for Ukraine".