WASHINGTON (Reuters) – The U.S. Treasury Department on Tuesday imposed sanctions on a Chinese national, accusing him of trafficking fentanyl to the United States.

It said in a statement that Taotao Zhang, a chemist and chemical supplier, had shipped illicit synthetic opioids to the United States. The Treasury also blacklisted Hong Kong-based Allyrise Technology Group Co, Limited, of which Zhang is director, accusing it of being a front company for his financial transactions.

Fentanyl is a cheap opioid painkiller 50 times more potent than heroin that has played a major role in an opioid crisis in the United States, where more than 28,000 synthetic opioid-related overdose deaths were recorded in 2017.

U.S. officials say China is the main source of illicit fentanyl. President Donald Trump has accused Chinese President Xi Jinping of failing to meet promises to help stop the flow of the drug into the United States, a charge Beijing rejects.

“The United States remains committed to protecting vulnerable Americans by targeting individuals peddling this deadly drug,” Treasury Deputy Secretary Justin Muzinich said.

Tuesday’s action freezes any U.S. assets of Zhang and the Hong Kong-based company and generally bars Americans from dealing with them.

The Treasury’s Office of Foreign Assets Control said it coordinated the move with the U.S. Attorney’s Office for the District of New Jersey and the Drug Enforcement Administration.

(Reporting by Daphne Psaledakis; editing by Grant McCool)