Acting President Han Duck-soo spoke on the phone with United States President Joe Biden on Sunday and pledged efforts to maintain and develop the South Korea-U.S. alliance.

Han made the vow during the phone call after the National Assembly passed a motion on Saturday to impeach President Yoon Suk Yeol over his martial law declaration on December 3.

During the phone talks, Han said that administration of state affairs will be conducted strictly in accordance with the Constitution and the law, and that the government will carry out its foreign and security policies without any disruptions.

Han reportedly discussed the domestic situation after Yoon's impeachment vote, strengthening the South Korea-U.S. alliance and the North Korean nuclear issue with Biden.

The acting president stressed the need to strengthen the combined South Korea-U.S. defense posture amid the growing threats from North Korean nuclear weapons and the deepening cooperation between North Korea and Russia. 

In response, Biden reportedly expressed his trust in South Korea's democracy and reaffirmed the "ironclad" alliance between the two nations, vowing to work together with Seoul to develop and strengthen the South Korea-U.S. alliance and trilateral cooperation with Japan.