China will designate fentanyl as a controlled substance after President Donald Trump and Chinese President Xi Jinping met at the G-20 summit in Argentina on Saturday.
The new classification in China means that anyone selling the drug to the U.S. "will be subject to China's maximum penalty under the law," according to a White House press statement.
The U.S.-China Economic and Security Review Commission lists China as the main source of illicit fentanyl being shipped to the U.S.
Fentanyl is an opioid that can be around 100 times stronger than morphine. Originally designed for use with cancer patients, in 2016 it surpassed heroin as the leading cause of drug overdose deaths in the U.S.
Last year, President Trump declared the opioid crisis a public health emergency.
Additional reporting by Newsy affiliate CNN.