HONG KONG — The executive in charge of Facebook’s efforts to court China has left the company, a fresh setback for the social network as it seeks to get its products into China’s huge internet market.

Wang-Li Moser, who as Facebook’s lead liaison with Beijing had become a symbol of its ambitions in the country, resigned in December, according to two people familiar with the matter.

Ms. Moser had been brought in from Intel to professionalize Facebook’s efforts to court China’s government. Her job was a tough one. She set up and presided over negotiations between China’s most powerful officials and a social network that many of them believed could be perilously destabilizing.

She also had to manage broader trade and security frictions between China and the United States. China blocks Facebook and most other major American internet companies, fearing the products could be used to undermine the government. Google, Twitter and Snapchat are all inaccessible within China. Apple and Amazon must use local partners to offer cloud services.