Acting President Han Duck-soo held phone talks with US President Joe Biden on Sunday and vowed to maintain and develop the two countries' alliance, his office said.

Han held the 16-minute phone conversation with Biden after President Yoon Suk Yeol was impeached by the National Assembly on Saturday over his short-lived imposition of martial law on Dec. 3.

"Our government will carry out our diplomatic and security policies without disruption and work to ensure that the South Korea-US alliance continues to be maintained and developed without wavering," he said, according to his office.

Han stressed the importance of solidifying the combined South Korea-US defense posture in the face of common challenges, such as the nuclear threat posed by North Korea and the deepening cooperation between Moscow and Pyongyang.

He also explained that all state affairs will be run strictly in accordance with the Constitution and the law.

Biden thanked Han for the explanation and voiced confidence in South Korea's democracy while also noting its resilience, according to Han's office.

Biden said "the ironclad South Korea-US alliance remains unchanged and that he will continue to work together with the South Korean side for the development and strengthening of the South Korea-US alliance and South Korea-US-Japan cooperation," it said.

Han thanked Biden for his attention and efforts in dramatically developing the bilateral alliance and trilateral cooperation with Japan during his term. Biden vowed to continue to support the development of the alliance.

Han, as prime minister, assumed office as acting president immediately after Yoon was suspended from his duties following his impeachment. (Yonhap)