MOSCOW, Mar. 13 (Reuters) - President Vladimir Putin said on Thursday that Russia supported a U.S. proposal for a ceasefire in Ukraine in principle, but sought a number of clarifications and conditions that appeared to rule out a quick end to the fighting.

Russia's invasion of Ukraine in February 2022 has left hundreds of thousands of dead and injured, displaced millions of people, reduced towns to rubble and triggered the sharpest confrontation for decades between Moscow and the West.

Putin's heavily qualified support for the U.S. ceasefire proposal looked designed to signal goodwill to Washington and open the door to further talks with U.S. President Donald Trump.

But Putin said many crucial details needed to be sorted out and any agreement must address the root causes of the conflict. Russia called its 2022 invasion a "special military operation" designed to "denazify" Ukraine and halt an expansion of NATO.

"We agree with the proposals to cease hostilities," Putin told reporters at the Kremlin. "The idea itself is correct, and we certainly support it."

"But we proceed from the fact that this cessation should be such that it would lead to long-term peace and would eliminate the original causes of this crisis."

He went on to list a slew of issues he said needed clarifying and thanked Trump, who says he wants to be remembered as a peacemaker, for his efforts to end the war. Both Moscow and Washington now cast the conflict as a deadly proxy war that could have escalated into World War Three.

Trump, who said he was willing to talk to the Russian leader by phone, called Putin's statement "very promising" and said he hoped Moscow would "do the right thing."

Trump said Steve Witkoff, his special envoy, was engaged in talks with the Russians in Moscow on the U.S. proposal, which Kyiv has already agreed to.

The U.S. president said those discussions on Thursday would show if Moscow was ready to make a deal.

"Now we're going to see whether or not Russia is there, and if they're not, it'll be a very disappointing moment for the world," he said.

Ukrainian President Volodymyr Zelenskiy said Putin was preparing to reject the ceasefire proposal but was afraid to tell Trump.

"That's why in Moscow they are imposing upon the idea of a ceasefire these conditions, so that nothing happens at all, or so that it cannot happen for as long as possible," Zelenskiy said in his nightly video address.

Photo from Reuters