Beijing remains committed to working with Washington to help solve the problem of fentanyl, a leading contributor to overdose deaths in the United States, but the root cause of the crisis lies at home, not in China, the Chinese embassy in the US said on Thursday.

The embassy said in a statement that some US politicians and media claim, "American fentanyl mainly (originates) from China", "Chinese fentanyl precursors flow into the United States via Mexico" and that China often delays the requests from the US side.

An embassy spokesperson called the claims "disinformation", saying that it is "disappointing" given all the goodwill and sincerity of the Chinese side, its strenuous efforts and huge sacrifices, as well as the great achievements of China-US cooperation in drug control.

Up to now, China has not found any scheduled precursor chemicals trafficked to Mexico or received any notification from the Mexican side about seizing scheduled chemicals originating from China, according to the embassy statement.

"Such made-up allegations show zero sense of responsibility toward American fentanyl abuse victims and their families, and seriously mislead the Chinese and American people," the spokesperson said.

"They are not in the least helpful for the United States to solve its drug problem and should be rectified as soon as possible," he added.

Synthetic opioids — primarily illicit fentanyl — remain the largest cause of overdose deaths in the United States, according to the US Centers for Disease Control and Prevention, which reported more than 93,000 drug overdose deaths in 2020, of which an estimated 69,710 were opioid overdoses, up by 30 percent from 2019.

"The Chinese side empathizes with the American people who are suffering from the opioid crisis and has been offering sincere and law-based assistance to the international community, including the United States, in dealing with fentanyl abuse," the spokesperson said.

As the biggest producer and user of fentanyl drugs in the world, the US has a fentanyl problem more rampant than in other countries, but it has not officially scheduled all fentanyl substances permanently yet, noted the Chinese embassy statement.

"The reasons behind are worth pondering. Here, we urge the US side to permanently schedule fentanyl substances as soon as possible," the spokesperson said.

In the US, drugs, substances, and certain chemicals used to make drugs are classified into five distinct categories or schedules depending upon the drug's acceptable medical use and the drug's abuse or dependency potential. The abuse rate is a determinate factor in the scheduling of the drug, according to the United States Drug Enforcement Administration.

In contrast, the Chinese government took the lead globally in officially scheduling fentanyl substances as a class on May 1, 2019, though there was no large-scale abuse or prominent hazards of them in China.

Before that, from 2017 to 2018, China scheduled six fentanyl substances and two precursor chemicals in two actions, which was more than the number of varieties listed by the United Nations at that time, according to the embassy.

Since the scheduling of fentanyl substances, there have been "close, candid and in-depth coordination" between Chinese authorities and US partners including the White House Office of National Drug Control Policy, the International Narcotics and Law Enforcement Affairs Bureau of the State Department and the Drug Enforcement Administration, according to the embassy.

It said that China has intensified its crackdown on online fentanyl sales and mandated its postal and parcel industry to take specific measures, such as ramping up inspection of US-bound parcels, to combat the trafficking of fentanyl substances and other scheduled chemicals.

Those measures have produced "notable" results and have been widely recognized by US law enforcement partners, who have expressed appreciation on many occasions and called drug control a highlight in bilateral law enforcement cooperation, the spokesperson said.

The spokesperson cited the latest briefing from the US side as saying that since September 2019, the US has not seized any fentanyl and its analogues originating from China.

"We want to remind the US side that the root cause of its fentanyl abuse problem is in itself. Blaming others is not conducive to solving the problem.

"It would be purely wrong to groundlessly criticize China and spread disinformation while appreciating China for support and help. This would only set up obstacles to our cooperation," the spokesperson said.

The spokesperson also noted that the addition of the US Commerce Department last May of the Institution of Forensic Science of the Ministry of Public Security and the National Narcotics Laboratory into its "entity list" has "seriously" affected China's examination and identification of fentanyl substances and hindered the operation of its fentanyl monitoring system.

"China urges the US side to correct this wrong practice as soon as possible," the spokesperson said.