BEIJING (AP) — China is designating all fentanyl-related drugs, as a group, as controlled substances — a step U.S. officials have long advocated as a way to stem the flow of lethal opioids from China.

Chinese officials announced the move on Monday and said it would become effective May 1.

U.S. officials hope that expanding controls to all varieties drugs that mimic fentanyl will help end the game of regulatory whack-a-mole with chemists who can manufacture novel opioids faster than they can be regulated.

The sweeping change in the way China regulates synthetic opioids makes good on a pledge Chinese President Xi Jinping made to President Donald Trump during the G-20 summit in Argentina last year. At the time, Trump said it could be “a game changer.”