WASHINGTON -- The United States will work to promote cooperation between South Korea and Japan as it sees trilateral cooperation between the two countries and the US as vital to facing regional challenges such as North Korea, a ranking US diplomat said Wednesday.

Sung Kim, acting assistant secretary of state for East Asian and Pacific affairs, said cooperation between South Korea and Japan is more important to the US than any other relationship.

"The Biden-Harris administration is committed to strengthening America's relationship, not only with our allies but also relationships among them," Kim told a webinar hosted by the Center for Strategic and International Studies, a Washington-based think tank.

"None are more important than Japan and the Republic of Korea," he added, referring to South Korea by its official name.

Kim's remarks came after he held his first three-way discussion with his South Korean and Japanese counterparts.

"During this productive discussion we stressed the importance of continued close coordination and expressed our continued commitment to complete denuclearization and peace and stability on the Korean Peninsula," he said of the three-way virtual meeting, held on Feb. 18.

Seoul-Tokyo relations have steadily deteriorated since mid-2019, when Japan imposed restrictions on South Korea-bound shipments of three key materials used to produce semiconductors and display panels, both key export items for South Korea.

Japan has also removed South Korea from its list of trusted trade partners in what was widely believed to be retaliation against a Seoul court ruling that ordered Japanese companies to pay compensation to South Korean workers forced into free labor during World War II.

Their bilateral relations deteriorated to even lower levels this year when a Seoul court ruled in favor of 12 former Korean sex slaves of the Japanese military seeking damages from the Japanese government.

Kim did not touch on the history issues in Wednesday's webinar but stressed the importance of cooperation between the countries.

"We will explore opportunities to expand cooperation in areas such as tackling COVID-19 and addressing climate change, and our working together to reinvigorate trilateral cooperation on the North Korea challenge," he said. (Yonhap)