Far-right groups are preparing to rally in the north-western US city of Portland, Oregon, amid fears of clashes with left-wing counter-protesters.
Police are expected to mount a major operation to keep the two sides apart.
The stated aim of the far-right gathering is to urge that the antifa (anti-fascist) movement be declared a domestic terror organisation.
Portland, one of the most liberal cities in the US, is regarded as an antifa stronghold.
One of the groups behind Saturday’s far-right rally is called Proud Boys, which says it is an organisation for young “Western chauvinist” men. The Southern Poverty Law Center, a major US civil rights organisation, has classified it as a hate group.
Proud Boys says incidents of violence allegedly involving members of the loosely organised antifa movement, an international coalition of militant activists and protesters opposed to the far right – justifies a ban.
Members of the local Rose City Antifa group are expected to mount a counter-demonstration in the city.
A statement on its website accuses far-right groups of planning “to bring their branded political violence to our streets” and encourages people “to defend Portland against far-right attack”.
Tina Jones, a spokeswoman for the Portland Police Bureau, said the city had received no permit applications for large public rallies on Saturday.
President Donald Trump urged the Portland mayor to do his job “properly”.
And he indicated that naming antifa “an organisation of terror” was being considered.
Mr Trump has previously mentioned white supremacists as well as antifa as being a major issue.