BEIJING/MOSCOW (Reuters) - China and Russia held off congratulating U.S. President-elect Joe Biden on Monday, with Beijing saying it would follow usual custom in its response and the Kremlin noting incumbent Donald Trump’s vow to pursue legal challenges.Democrat Biden clinched enough states to win the presidency on Saturday and has begun making plans for when he takes office on Jan. 20. Trump has not conceded defeat and plans rallies to build support for legal challenges. Some of the United States’ biggest and closest allies in Europe, the Middle East and Asia quickly congratulated Biden over the weekend despite Trump’s refusal to concede, as did some Trump allies, including Israel and Saudi Arabia. German Chancellor Angela Merkel on Monday called for the European Union and United States to work “side by side”, holding up Biden as an experienced leader who knows Germany and Europe well and stressing the NATO allies’ shared values and interests.