WASHINGTON: Russian President Vladimir Putin is "trying to find some oxygen" by floating a 36-hour ceasefire, US President Joe Biden told reporters at the White House on Thursday when asked about Moscow's truce proposal.

The Kremlin said Putin had ordered a ceasefire from midday on Friday after a call for a Christmas truce from Patriarch Kirill of Moscow, the head of the Russian Orthodox Church.

Putin orders ceasefire in Ukraine on January 6-7: Kremlin

Ukraine spurned the offer from Putin for the 36-hour ceasefire over Orthodox Christmas, saying there would be no truce until Russia withdraws its invading forces from occupied land.