BEIJING (AP) — The U.S. ambassador to China appears to be leaving his post, based on tweets by Secretary of State Mike Pompeo.

Pompeo thanked Ambassador Terry Branstad for more than three years of service on Twitter on Monday. There was no immediate confirmation from the State Department.

Branstad was embroiled in a recent controversy when China’s official People’s Daily newspaper rejected a column that he had submitted. It wasn’t clear if his apparent departure was related to the piece.

Pompeo said in a follow-up tweet that Branstad had contributed to a rebalancing of U.S.-China relations to make them results-oriented, reciprocal and fair.