A White House official declined to lay out the specifics of any potential U.S. response, but said that Biden was "detailed" and "direct" with the Chinese leader.
It's been more than two years since leaders of the United States and China met face-to-face. This meeting will be virtual, not in person, and comes at a time of high tensions.
The Chinese leader says a "peaceful reunification," rather than one through military force, would benefit both China and Taiwan. Tensions between the two are the highest in decades.
In a fiery speech at Tiananmen Square, Communist Party Chairman Xi Jinping vowed to keep an iron grip on Hong Kong and to conquer Tiawan, and warned foreign forces against trying to bully China.
Chinese officials boast their campaign against "evil" has busted over 50,000 supposed criminal organizations, but experts warn it has served another function: consolidating power.
Leaders in the Kremlin and Beijing, as well as in Mexico and Brazil, have conspicuously not congratulated the president-elect, instead waiting for legal challenges to be resolved.
President Trump counts several world leaders as his fans, many of them authoritarians, nationalists or populists. Some may struggle to stay as friendly with the White House if he loses the election.