Russian President Vladimir Putin says Russia is willing to work with whomever is officially declared the next president of the United States, but that he won't offer congratulations until the winner is formally decided or a candidate concedes.

Putin's remarks broadcast on Sunday on state television reiterate earlier Kremlin comments on why Putin had not congratulated Joe Biden after major news organisations called him president-elect, as did many other world leaders.

"We are just waiting for the end of the internal political confrontation," Putin said, referring to Republican challenges to the vote count.

"We will work with any person who will be given the trust of the American people. But who will be given this trust? It must either be indicated by political custom when one of the parties recognises the victory of the other, or the final results of the elections are summed up in a legitimate, legal way," he said.

Earlier this month, China finally congratulated Biden nearly a week after he was declared winner of the American election.

“We respect the choice of the American people. We express our congratulations to Biden and Harris,” foreign ministry spokesman Wang Wenbin had said at a regular press briefing, referring to incoming vice president Kamala Harris.

Wang had said China understands “the result of the US election will be determined in accordance with US laws and procedures”.