The US ambassador to China who oversaw diplomatic dramas including an activist's escape from house arrest to find refuge in the embassy is to resign, he said in a statement Wednesday.

Gary Locke, the first ethnic Chinese to hold the post, will step down early next year to "rejoin my family" in his home town of Seattle, he said, calling his two and a half years in the job "an immense and rewarding challenge".

Locke, whose grandfather immigrated to America from the southern province of Guangdong, drew attention from his arrival in Beijing in August 2011 as the first ethnic Chinese to hold the prestigious post.

He also gained a following as a humble dignitary -- a stark contrast to Chinese officials -- after being seen carrying his own luggage and travelling in a regular car.

In February 2012 a diplomatic drama erupted when senior Chinese official Wang Lijun fled to the US consulate in the southwestern city of Chengdu from his powerful boss Bo Xilai, then head of the nearby metropolis of Chongqing.

Wang soon left the premises to be dealt with by Chinese authorities and was last year sentenced to 15 years in prison.

A few months later Locke handled a tougher diplomatic standoff when blind rights activist Chen Guangcheng escaped house arrest in the eastern province of Shandong and sought refuge at the US embassy in Beijing.

After days of tense negotiations involving US Secretary of State Hillary Clinton, Chen and his family were allowed to go to the US.

Locke rushed back from a holiday in Bali and spent several hours each day talking to the activist, the New York Times reported at the time.

The US ambassador garnered attention again in June 2013 by becoming the first holder of the post in three years allowed to visit Tibet, where rights groups complain of Chinese suppression of the ethnic minority, claims that Beijing denies.

Authorities closed off the area after deadly 2008 riots and Locke arrived amid a string of Tibetan self-immolations that picked up in 2009 in the region and nearby provinces.

In his brief statement, Locke mentioned visiting Tibet and meeting human rights lawyers as measures that "advanced American values".

A former commerce secretary, he also touted his promotion of American businesses in China and Chinese investment in the US.