A former newspaper journalist, Yamamoto has previously worked on the department's Korea, China and Indonesia desks. She has also served as director of the Office of Economic Policy in the department's Bureau of East Asian and Pacific Affairs.

Her overseas assignments include postings in the Philippines, New Zealand, Trinidad and Brazil.

In Seoul, Yamamoto handled trade issues, including the renegotiation of the South Korea-US free trade agreement and economic sanctions on North Korea, according to sources familiar with her role.

Her appointment nearly completes the lineup of senior US diplomats handling Korea affairs.

In recent months, former Ford Motor Vice President Stephen Biegun took office as US special representative for North Korea, and Harry Harris filled a longstanding vacancy as US ambassador to Seoul.

Marc Knapper, who until recently served as acting US ambassador to South Korea, also moved into the job of acting deputy assistant secretary for Korea and Japan issues.

Still to be named is the assistant secretary of state for East Asian and Pacific affairs, the top US diplomat for the region. (Yonhap)