President Donald Trump talks to reporters as he departs for travel to the G-20 summit in Argentina from the White House in Washington, November 29, 2018.

President Donald Trump on Wednesday called on China to seek the death penalty for distributors of fentanyl, an opioid linked to thousands of deaths in the United States each year. China is the largest source of the drug.

"If China cracks down on this 'horror drug,' using the Death Penalty for distributors and pushers, the results will be incredible!" the president wrote in a post on Twitter. He said that an agreement about the drug reached with his Chinese counterpart Xi Jinping was "very exciting," and suggested it could be a "game changer."

Tweet1

Tweet

The Trump administration has made it a top priority to tackle Chinese exports of fentanyl and its precursor chemicals. Fentanyl is a synthetic opioid that can be as much as 100 times stronger than morphine.

Over the weekend, the White House alluded to the possibility that China would seek the death penalty for distributors.

In a statement, the White House said Xi had agreed to designate fentanyl a controlled substance, "meaning that people selling Fentanyl to the United States will be subject to China's maximum penalty under the law."

The maximum sentence for drug distribution in China is the death penalty.

But it was not immediately clear that the U.S. and China had reached a significant agreement.

Fentanyl has been designated as a controlled substance in China for years.

In its own statement, the Chinese foreign ministry said that China would designate all "fentanyl-like substances" as controlled substances "and start working to adjust related regulations." The statement did not say what penalties the government would seek. Experts have noted that Chinese officials have shown a willingness to work with their American counterparts, but that regulations remain "slow and ineffective."

In testimony to lawmakers in September, Paul Knierim, a DEA official, said the drug is made illicitly in China by some of China's 160,000 chemical companies.

"Although the majority of chemical production is intended for legitimate use, illicit drug manufacturers directly source or divert their chemicals from China for their drug production," he said.

The Chinese pharmaceutical industry is the second largest in the world, after the United States, generating more than $100 billion in revenue.

The exact amount of Chinese exports of fentanyl and related substances is unknown. But, in a 2016 letter to the United Nations secretary-general, then-Secretary of State John Kerry that the Obama administration had identified at least 257 suppliers of two key precursor chemicals. More than half those suppliers were in China.

The high potency of the drug lends it deadly force even at small doses. Just $5,000 can buy enough fentanyl on the Chinese market to provide lethal doses to half a million people, according to a report by the U.S.-China Economic and Security Review Commission.

China used the death penalty more than any other country in 2017, according to Amnesty International. The rights group cautioned, however, that "the true extent of the use of the death penalty in China is unknown as this data is classified as a state secret."

WATCH: These party drugs could become the answer for clinically depressed patients