Washington stations about 28,500 troops in South Korea to protect it from North Korea, its nuclear-armed neighbour.
The United States and South Korea have long carried out joint exercises, infuriating the North, which views them as rehearsals for invasion and has frequently conducted weapons tests in retaliation.
Biden has also fostered the relationship between Washington, Seoul and Tokyo as a bulwark against both North Korea and an increasingly assertive China.
Earlier on Tuesday, the US State Department echoed the White House concern, with Deputy Secretary of State Kurt Campbell stating that Washington has “every hope and expectation that any political disputes will be resolved peacefully and in accordance with the rule of law”.
“I do want to underscore that our alliance with the ROK is ironclad, and we stand by Korea in their time of uncertainty,” he said.
Yoon has been a close ally of the United States, with Biden welcoming him on a state visit last year and South Korea in March hosting a global democracy summit, a signature idea of the outgoing US administration.
In the wake of Donald Trump’s election victory in November, the South Korean president congratulated the Republican, saying he hoped to work closely with the incoming US administration.
