WASHINGTON (AFP) - The top US diplomat for Asian affairs, Kurt Campbell, stepped down from his post on Friday after almost four years in the job helping to steer America's pivot to Asia, a US official said.

Mr Campbell has served as assistant secretary of state for East Asian and Pacific Affairs since June 2009, and has criss-crossed the region since taking over from his predecessor Christopher Hill.

He will be replaced by his deputy Joe Yun until a new assistant secretary is nominated by President Barack Obama, a top US official said, asking not to be named.

Mr Campbell, an academic and former naval officer, was known for his extensive knowledge of Asia and his boundless energy in engaging with his Asian counterparts under former secretary of state Hillary Clinton.

"This position is the key face of US diplomacy in Asia and often Washington's main strategic thinker about Asia," The Australian daily newspaper wrote in a weekend editorial.

"Campbell was so effective because of his deep knowledge of Asia, larger-than-life personality, endless energy, diamond-hard mind, sense of strategic realities and closeness to Clinton."