Sen. Chuck Schumer says he’ll “watch China like a hawk” after Chinese President Xi Jinping agreed to stop the flow of fentanyl into the U.S.

Most of the fentanyl that comes into the U.S. is made out of chemicals that come from Chinese companies.

As part of the agreement, China will enforce laws and regulations against those Chinese companies. But, Schumer warns, we’ve been burned before.

“It’s rare to get China to make commitments like this, but we cannot let it stop at words. We have to see results. In the past, China has made commitments and not lived up to them,” Schumer said.

The senator says China has already agreed to resume counter-narcotic operations in cooperation with U.S. officials.