Trump said on Truth Social that he was "designating" the movement as a terrorist organization. "I will also be strongly recommending that those funding ANTIFA be thoroughly investigated in accordance with the highest legal standards and practices," Trump wrote.
It was not clear what legal weight Trump's proclamation carried. Antifa is a loosely organized ideological movement without a clear leadership structure or hierarchy, experts said.
A day after Utah prosecutors unveiled formal charges against the suspect in the assassination of Charlie Kirk, no evidence has emerged connecting 22-year-old Tyler Robinson with any outside group. Questions also remain about his precise motives.
Trump and senior officials have repeatedly blamed left-wing groups for creating an atmosphere of hostility towards conservatives before Kirk's assassination.
The White House is preparing an executive order on political violence and hate speech, a Trump administration official said earlier on Wednesday.
U.S. Vice President JD Vance, in an interview with Fox News on Wednesday, repeatedly blamed what he called left-wing political radicalization for the assassination.
He said the White House was working hard to ensure that "funding networks for left-wing violence" are going to be treated like a terrorist organization.
Critics say that Trump is using Kirk's assassination as a pretext to crack down on political opponents.
At the time, legal experts said such a step lacked a basis in law, would be hard to execute, and raised free-speech concerns, given that subscription to an ideology is not generally considered criminal.
The White House did not immediately respond to a request for further details on Wednesday.
