Russian President Vladimir Putin is waiting for the official results of the US presidential election to be announced before congratulating the winner, a Kremlin spokesperson said Monday.
Joe Biden was widely declared to have been elected as US president over the weekend but his victory has been disputed by incumbent Donald Trump.
Trump is launching legal challenges against the results in several key battleground states, after making unsubstantiated claims of electoral fraud.
"We believe it is correct to wait for the official results of the elections that have taken place. I'd like to remind you that President Putin has repeatedly said that he will respect the choice of the American people whatever it may be," Russian presidential spokesman Dmitry Peskov told reporters.
The head of the Russian electoral commission, Ella Pamfilova, on Monday said that postal voting in the US has left "immense spaces" for possible electoral fraud.
Putin was one of the first leaders to congratulate Trump on his victory in 2016, with a message a little over an hour after US media projections said that he had won.
But having recently named Russia as the biggest threat to the US, Biden has been an outspoken critic of Moscow.
Peskov said Putin is "ready to work with any president of the United States", adding Russia hopes it will be possible to have "a dialogue and agree on ways to normalise bilateral relations" with the next president.
Russian-American relations have continued to deteriorate since Moscow was accused of interfering in the 2016 presidential election to promote the election of Trump.
The American billionaire has always denied having benefited from Russian efforts, as has Putin, despite the findings of a US investigation that led to sanctions against Russia.
Biden's election is likely to further increase tensions, as the former vice-president has promised to be tougher with Moscow than his predecessor.