New U.S. Secretary of State Marco Rubio held talks with his South Korean and Japanese counterparts for the first time on Wednesday, agreeing to maintain close cooperation on North Korean nuclear threats following Donald Trump’s inauguration.

Rubio spoke with South Korean Foreign Minister Cho Tae-yul by phone and emphasized that the U.S.-ROK alliance is the “linchpin of peace and security not only on the Korean Peninsula but also in the region,” according to Seoul’s foreign ministry on Thursday.

“Secretary Rubio affirmed that the U.S. commitment to the defense of South Korea remains as firm as iron, and the two