Washington DC - Secretary of State Marco Rubio on Wednesday steered clear of calling Russian President Vladimir Putin a "war criminal," saying the priority was negotiations to end the Ukraine conflict.

In a fiery congressional hearing, Democratic Representative Bill Keating recalled Rubio's heated criticism of Putin's record when the top US diplomat served as a senator, and asked him if he still believed Putin is a "war criminal."

"Crimes have been committed in the war on Ukraine, and there will be accountability for that, but our goal right now is to end that war," Rubio said.

"Because let me tell you, every single day that that war goes on, people are killed, more people are maimed and, frankly, more war crimes are being committed," he said.

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Keating accused Rubio of being "inconsistent" and "equivocating."

Rubio later responded to a fellow Republican by saying there was a value in speaking to Russia.

"If there had not been communications between the US and Russia in 1961," Rubio said, "the world could have ended during the Cuban Missile Crisis."

President Donald Trump spoke Monday by telephone to Putin and Ukrainian President Volodymyr Zelensky in his latest effort, so far unsuccessful, to end the war.

Putin, who had faced international isolation during former President Joe Biden's administration, has rebuffed US calls backed by Ukraine for a 30-day ceasefire.

Tens of thousands have died, mainly civilians, since Russia invaded Ukraine in February 2022.

Early in the war, dozens of civilians were found dead in the Kyiv suburb of Bucha following a months-long occupation by Russian forces.

Putin faces an arrest warrant from the International Criminal Court over the transfer of children from Russian-occupied parts of Ukraine into Russia.

Prior to Wednesday's hearing, Rubio had publicly called Putin a war criminal, including one X post from 2022 where he wrote that "The suffering in Ukraine because of the war criminal Putin is obvious to all".