Plastic bags of Fentanyl are displayed on a table at the US Customs and Border Protection area at O’Hare international airport in Chicago, Illinois.

China is suspected of being the main source of a powerful painkiller that has caused record overdose deaths in the US.

China has announced it will crack down on all fentanyl-like substances, following US pleas for Beijing to control a drug fuelling a deadly opioid crisis.

But a senior official repeated China’s denial of responsibility for the US’s deadly opioid crisis, which he blamed instead on American culture.

“Some people link drug consumption with freedom, individuality and liberation,” said Liu Yuejin, deputy director of the National Narcotics Control Commission. “If the United States truly wants to resolve its fentanyl abuse problem, it needs to strengthen its domestic work.”

China is suspected of being the main source of a powerful painkiller 50 times stronger than heroin that has caused record overdose deaths in the United States.

Fentanyl has been tied to already tense bilateral relations, with the US trade representative, Robert Lighthizer, saying he hopes to include China’s commitments to curb the drug in any agreement to end the two countries’ bitter trade war.

In December, Trump said the move against the “horror drug” could be a “game changer” because China has the death penalty for major narcotics offences.

By designating all fentanyl analogues as controlled substances from 1 May, China aims to prevent smugglers from skirting the law by changing formulas to make drugs similar to the painkiller.

Liu told reporters that US concerns had been “resolved. All resolved.”

But Liu repeated China’s denial of responsibility for the US’s deadly opioid crisis, saying US allegations of large scale trafficking from China “lack evidence and are contrary to the facts”.

“We believe that the United States itself is the main factor in the abuse of fentanyl there,” Liu said, adding that American culture was partly to blame.

Liu said China “cannot possibly be the major source to the US”.

Instead, Liu blamed American’s abuse of prescription opioids, pharmaceutical industry influence, US pharmacies and doctors’ “excessive prescription”, lax enforcement and American culture conflating drugs with “freedom, individuality and liberation”.

“If the US really wants to resolve the fentanyl substance problem, they have more work to do domestically,” he said.

A US congressional inquiry into the use of fentanyl in the United States found in 2018 that the substance could easily be bought online from Chinese “labs” and mailed to the United States.

Liu said Chinese authorities will urge courier companies to implement real-name registration for parcels, stepping up customs checks for high-risk international packages and enhancing enforcement co-operation.

Mike Vigil, former head of international operations for the US Drug Enforcement Administration said that the measures announced on Monday would have a major impact, but he agreed that “corporate greed in pharmaceutical industry” and overprescription of opioids had driven a lot of the epidemic in the US.

“If China stems the movement of fentanyl and other synthetic opioids to the United States it would have a huge impact, but it would not stop the epidemic,” he said.