WASHINGTON, June 30 (Xinhua) -- Retired Admiral Harry Harris was sworn in as the U.S. ambassador to South Korea on Saturday, the White House said.

U.S. Secretary of State Mike Pompeo congratulated Harris, 61, in a tweet published on Saturday afternoon, saying that "a lot of work ahead" waiting for Harris, including the denuclearization of the Korean Peninsula.

Harris, who previously served as the commander of U.S. Pacific Command, was confirmed by the Senate on Thursday.

The post of the U.S. ambassador to South Korea was vacant for more than a year after Trump took office in 2017.

It was reported that the White House withdrew its nomination of Victor Cha, a veteran Korea expert, in January because of Cha's opposition to military options against Pyongyang.