Russian President Vladimir Putin won’t congratulate President-elect Joe Biden until legal challenges to the U.S. election are resolved and the result is official, the Kremlin announced Monday.

Putin is one of a handful of world leaders who have not commented on Biden’s victory, which was called by major news organizations on Saturday. But President Donald Trump’s team has promised legal action in the coming days and refused to concede his loss, while alleging large-scale voter fraud, so far without proof.

When Trump won in 2016, Putin was prompt in offering congratulations — but Trump’s challenger in that election, Hillary Clinton, also conceded the day after the vote.

Putin’s spokesman Dmitry Peskov told reporters Monday that this year is different.

“Obviously, you can see that certain legal procedures are coming there, which were announced by the incumbent president — therefore this situation is different, so we consider it correct to wait for the official announcement,” he said.

The leaders of China, Brazil and Turkey also are holdouts in offering congratulations. And Mexican President Andrés Manuel López Obrador also said he would wait to comment until the legal challenges were resolved.