Thornton, who joined the Foreign Service in 1991, has spent the last 20 years working on US policy in Eurasia, focused on the countries of the former Soviet Union and East Asia. As principal deputy assistant secretary, she is responsible for policy related to China, Mongolia, and Taiwan.

Russel's departure has been expected as with the cases of all such senior position holders during the previous administration.

Russel assumed the post in 2013 after serving as senior Asian affairs director at the National Security Council. While there, he helped formulate Obama's strategic "rebalance" or "pivot" to Asia policy, including efforts to strengthen alliances, deepen US engagement with multilateral organizations, and expand cooperation with emerging powers in the region.

At the institute, Russel will work to build inclusive solutions and greater collaboration between the US and the Asia-Pacific region, the think tank said in a statement.

"Danny Russel is a first class American diplomat," said former Australian Prime Minister Kevin Rudd, who serves as ASPI president.

"Russel is respected across the Asia-Pacific as a 'straight-shooter' and will bring to the Asia Society Policy Institute a wealth of experience from his extensive work, over many years, with governments across Asia."

Russel said in the statement that he looks forward to joining the think tank.

"I value the chance to build on what America has accomplished with its partners in Asia -- truly transformative legacy," he said. (Yonhap)