Donald Trump said early on Thursday that he plans to designate antifa as a “major terrorist organization”.

Antifa, short for “anti-fascists”, is an umbrella term for far-left-leaning activist groups and is not a single entity. These are groups that resist fascists and neo-Nazis, especially at demonstrations.

It was unclear how the administration would label what is in effect a decentralized movement as a terrorist organization, and the White House on Wednesday did not immediately offer more details.

The US president, who is on a state visit to the UK, made the announcement in a social media post shortly before 1.30am Thursday local time. He called antifa a “SICK, DANGEROUS, RADICAL LEFT DISASTER”. He also said he will be “strongly recommending” that funders of antifa be investigated.

Antifa is a domestic entity and, as such, is not a candidate for inclusion on the state department’s list of foreign terror organizations. Dozens of groups, including extremist organizations like the Islamic State and al-Qaida, are included on that list. The designation matters in part because it enables the justice department to prosecute those who give material support to entities on that list even if that support does not result in violence.