WASHINGTON: US ambassador to China Terry Branstad is stepping down, Secretary of State Mike Pompeo announced Monday, at a time of increasingly strained ties between the world's two biggest economies.

Thanking Branstad for his service, Pompeo said in a tweet that he had "contributed to rebalancing US-China relations so that it is results-oriented, reciprocal, and fair."

In a statement, the US embassy in Beijing confirmed the departure, saying Branstad was retiring and would leave Beijing next month. It added that he had confirmed his decision to President Donald Trump by phone last week.

The 73-year-old had been in his post since May 2017.

"I am proudest of our work in getting the Phase One trade deal and delivering tangible results for our communities back home," the statement quoted him as saying.