President Donald Trump said he is designating the far-left anti-fascism movement Antifa as a terrorist organization, announcing the move on his Truth Social platform in the early hours of Thursday morning UK time.

It wasn’t immediately clear what mechanism Trump would use to make the designation, and Antifa lacks centralized structure or defined leadership, making it unclear who or what precisely would be targeted.

“I am pleased to inform our many U.S.A. Patriots that I am designating ANTIFA, A SICK, DANGEROUS, RADICAL LEFT DISASTER, AS A MAJOR TERRORIST ORGANIZATION,” Trump wrote. “I will also be strongly recommending that those funding ANTIFA be thoroughly investigated in accordance with the highest legal standards and practices. Thank you for your attention to this matter!”

A White House official told CNN, “This is just one of many actions the president will take to address left wing organizations that fuel political violence.”

Trump — who’s overseas for a formal state visit — signaled the move earlier this week in remarks from the Oval Office following the murder of conservative activist Charlie Kirk.