WASHINGTON — The Trump administration on Wednesday imposed sanctions on three Chinese nationals accused of trafficking synthetic opioids, stepping up efforts to curb the flow of fentanyl from China into the United States.

The move comes just weeks after President Trump accused China of not doing enough to stop the drug from entering the United States — one of several factors he cited as a reason for escalating his trade war with Beijing.

The Treasury Department’s Office of Foreign Assets Control, or OFAC, is placing sanctions on Fujing Zheng and the Zheng Drug Trafficking Organization along with Guanghua Zheng and Qinsheng Pharmaceutical Co., which support the organization’s activities. It also identified Xiaobing Yan as a “significant foreign narcotics trafficker.”

“The Chinese kingpins that OFAC designated today run an international drug trafficking operation that manufactures and sells lethal narcotics, directly contributing to the crisis of opioid addiction, overdoses, and death in the United States,” Sigal Mandelker, under secretary for terrorism and financial intelligence, said in a statement. “Zheng and Yan have shipped hundreds of packages of synthetic opioids to the U.S., targeting customers through online advertising and sales, and using commercial mail carriers to smuggle their drugs into the United States.”