BEIJING -- The U.S. government can do more to reduce demand for fentanyl and should stop shifting the blame onto others, China said on Monday, in another riposte to Trump administration criticism that China is not helping resolve the drug problem.

U.S. officials say China is the main source of illicit fentanyl and fentanyl-related substances that are trafficked into the United States, much of it through international mail. China denies that most of the illicit fentanyl entering the United States originates in China.

U.S. President Donald Trump this month accused Chinese President Xi Jinping of failing to meet his promises to crack down on the deluge of fentanyl and fentanyl analogues flowing into the United States. China labeled that “blatant slander”.

Fentanyl is a cheap, relatively easy-to-synthesize opioid painkiller 50 times more potent than heroin that has played a major role in a devastating U.S. opioid crisis.

Speaking at a daily news briefing, Chinese Foreign Ministry spokesman Geng Shuang said the government was playing a positive role is tackling the global drugs issue, and outlined the steps China had taken to control it.

The United States consumes 80 percent of the world’s opioids despite having only five percent of the population, Geng said.

“When it comes to reducing demand for fentanyl the U.S. government absolutely can do even more,” he added. “The United States should respect the facts, and stop pinning the blame on others.”

The U.S. Treasury last Wednesday imposed sanctions on three Chinese men accused of illegally trafficking fentanyl, acting three weeks after Trump accused China of reneging on pledges to stem the flood of the highly addictive synthetic opioid into the United States.

The dispute over fentanyl comes as the United States is in the middle of a major trade dispute with China.