The US ambassador to China on Wednesday accused the Asian power of failing to stop production of fentanyl, vowing to keep pressure to curb the drug which kills hundreds of Americans a day.

Speaking virtually to an audience in Washington,  Ambassador Nicholas Burns made clear that combatting the synthetic opioid -- a top priority for US lawmakers -- would be high on the agenda with Beijing.

China banned US-bound exports of fentanyl in 2019, a move hailed by the then administration of Donald Trump, but experts say it remains the source of precursor chemicals sent to traffickers in Mexico and Central America.

"We have been pushing very hard that the government of China use its considerable power to shut down the ability of these black-market Chinese firms to sell the fentanyl," Burns said.

"Frankly, we have not seen progress on this issue," he told the US Global Leadership Coalition, a nonpartisan group that promotes US funding on foreign affairs.

"We're not going to quit in raising this issue and expecting that the government of China will do the right thing," he said.

Burns raised the issue ahead of an expected visit to Beijing by Secretary of State Antony Blinken as the two powers look to keep tensions from spiraling out of control on several points of contention including Taiwan.

China in the past has denied responsibility for the fentanyl crisis, saying that the United States should look at its own societal issues and the role of the pharmaceutical companies.

More than 80,000 Americans died from opioid overdoses in 2021, with the number rising sharply over the past decade.

Among recent actions, the United States has slapped sanctions on Chinese companies seen as involved in trade of fentanyl, which can be up to 50 times more powerful than heroin.

A handful of Republican lawmakers have called for stronger action including even armed intervention against Mexican drug cartels.