(NewsNation) — In an effort to disrupt the supply chain of fentanyl, Mexico has asked China to do more to prevent the export of precursor chemicals used by cartels to manufacture the synthetic drug.

China responded to a desperate letter from Mexican President Andrés Manuel López Obrador, revealed this week, that asked the communist country to do more to stop the production of fentanyl in Mexico.

“We come to you, President Xi Jinping, for humanitarian reasons to help us control shipments of fentanyl that may be sent from China to our country. According to available information, it is produced in Asia and freely sold for export to Canada, the United States, and our country,” Obrador pleaded.

Only after several paragraphs of venting, López Obrador brings up China’s exports of fentanyl precursors, and asked him to help stop shipments of chemicals that Mexican cartels import from China.

“I write to you, President Xi Jinping, not to ask your help on these rude threats, but to ask you for humanitarian reasons to help us by controlling the shipments of fentanyl,” the Mexican president wrote.

China has taken some steps to limit fentanyl exports, but mislabeled or harder-to-detect precursor chemicals continue to pour out of Chinese factories. Efforts to keep precursor chemicals from being sold to those hoping to make illegal drugs have been complicated, in part because many of the chemicals also have legitimate uses.

China’s foreign minister pointed the finger back at Mexico, saying “we also hope that the Mexican side will take stronger measures in the fight against drugs.”

In recent months, Mexico has been hounded by U.S. lawmakers, especially Republicans, to do more to fight cartels and crack down on the flow of the deadly synthetic drug into the U.S. via the southern border.

The National Institute of Health estimates more than 70,000 Americans died from synthetic opioid overdoses in 2021, a skyrocketing majority of them caused by fentanyl.

Republican Sen. Lindsey Graham even sent a video straight to López Obrador.

“But I want to work with you to shut down these labs and the first problem that we’ve got to come to grips with is that the labs operate in Mexico and you’re doing nothing about it,” Graham said. “They get the precursor drugs from China and if you don’t change your policies we’re going to have to take matters into our own hands.”

Graham also tweeted plans to introduce legislation to address the scourge of fentanyl, which he hopes will gain bipartisan support.

The Associated Press contributed to this report.