The US Department of Homeland Security has issued a national terrorism advisory, warning of a heightened threat following the US election.
It said there was no information on a specific or credible plot.
But it said “individuals frustrated with the exercise of governmental authority and the presidential transition” could pose a threat.
It warned that the 6 January attack on the US Capitol by Trump supporters may have emboldened home-grown extremists.
The attack came as Congress was meeting to confirm Joe Biden’s election victory. Outgoing President Donald Trump had earlier addressed thousands of his supporters outside the White House and repeated unfounded claims that the election had been stolen from him.
He told them: “If you don’t fight like hell you’re not going to have a country any more.”
A crowd then made its way to the Capitol, overwhelming security and storming the building. Five people, including a Capitol Police officer, died in the riot.
Mr Trump has now been impeached by the House of Representatives for incitement and his trial in the Senate is due to start next month.
The advisory issued on Wednesday said that the department believed a heightened threat would persist in “the weeks following the successful presidential inauguration”.
“Information suggests that some ideologically-motivated violent extremists with objections to the exercise of governmental authority and the presidential transition, as well as other perceived grievances fuelled by false narratives, could continue to mobilise to incite or commit violence,” it said.
The advisory added that some “domestic violent extremists… may be emboldened” by the breach of the Capitol building “to target elected officials and government facilities”.
The attack on the Capitol sent shockwaves around the country and US authorities moved quickly to identify and arrest those responsible.
Prosecutors say they have so far identified 400 suspects and arrested 135 in connection with the violence.