US President Donald Trump and Russian President Vladimir Putin are set to speak by phone on Tuesday in a potentially crucial step toward halting the war in Ukraine, over three years into Moscow's invasion.
Both sides have expressed optimism about recent talks between Washington and Moscow but have agreed that only a top-level call could resolve the toughest sticking points on a 30-day truce, AFP reported.
Ukraine has agreed to the ceasefire -- yet both Kyiv and European capitals are skeptical that Putin may be stalling, and wonder whether Trump is willing to use leverage against a leader with whom he seems intent on restoring ties.
"We're going to have a very important call," Trump told reporters on Monday. "We're getting down to a very critical stage."
Trump added later on his Truth Social network that "many elements of a final agreement have been agreed to, but much remains.
"I look very much forward to the call with President Putin," he said.
Putin said last week he agreed with the idea of a ceasefire but warned he had "serious questions" about how it would be implemented that he wanted to discuss with Trump.
With Moscow occupying swathes of southern and eastern Ukraine, US officials have made clear that Ukraine would likely have to cede territory in any deal.
Trump said on Sunday that he and Putin would discuss "dividing up certain assets" including land and power plants: an apparent reference to the Moscow-controlled Zaporizhzhia nuclear plant in south Ukraine, Europe's largest.
US-Ukraine split
Trump's return to the White House has seen a total upending of US policy on Ukraine.
The US president stunned the world when he announced last month that he had spoken to Putin, in a call that broke Western efforts to isolate the Russian leader as long as his forces keep up their Ukraine invasion.
He has since said that he has spoken "numerous times" to the Russian leader, for whom he has repeatedly expressed admiration in the past, though none was officially announced.
Trump's special envoy Steve Witkoff held a three-hour meeting with Putin last Thursday in Moscow to present the details of the joint ceasefire plan, which envisages a 30-day pause in hostilities.
But as Washington's relations with Moscow have thawed, its ties with Ukraine have become far more complicated.
Trump had a televised shouting match with Ukrainian President Volodymyr Zelensky in the Oval Office on February 28 which led to the United States temporarily suspending its billions of dollars in military aid to Kyiv.
Zelensky later relented and agreed to both the ceasefire plan and a deal to give the United States preferential access to Ukraine's rare earth mineral deposits.
'Been through hell'
But Zelensky has still reacted with anger to Putin's recent statements, accusing him of wanting to prolong the fighting to improve Moscow's position on the battlefield.
Russia has been pressing ahead in several areas of the frontline for over a year.
Moscow has in particular boasted in recent days about ousting Ukrainian troops from Russia's western Kursk region -- which had been a major bargaining chip for Kyiv.
Concerns have mounted among Western allies that Trump is giving too much away to Putin without demanding any concessions from the wily Russian leader.
Trump has repeatedly said he wants to end the bloodshed whatever it takes -- but he is also keen to live up to his 2024 election campaign pledge that he would end the fighting quickly.
The president said last week that he could hit Russia with "devastating" economic sanctions if necessary but that he hoped he would not need to and that Putin would reach a deal.
The US president has meanwhile repeatedly boasted of a bond with Putin.
During the Zelensky row, Trump raged that "Putin went through a hell of a lot with me," referring to the investigation during his first term into whether his 2016 election campaign colluded with Moscow.
