The United Nations on Tuesday called on political leaders including US President Donald Trump not to incite violence, as Washington prepares for President-elect Joe Biden's inauguration.

Days after pro-Trump supporters smashed their way into the Capitol building in a bid to overturn Biden's election win, the UN was asking "political leaders not to encourage their followers to commit violence or to incite violence," UN spokesman Stephane Dujarric said.

He said the message was "universal", including for the US.

Democrats, who say Trump incited last week's riots, are this week attempting to get him removed from office through impeachment or other means.

US National Guard soldiers guard the US Capitol grounds
US National Guard soldiers guard the US Capitol grounds AFP / Daniel SLIM

Biden will be inaugurated in the US capital January 20 and federal and local authorities are scrambling to prevent a repeat of last week's deadly events that led to the deaths of five people.

According to US media reports, an internal FBI document warns that armed Trump supporters plan to participate in protests against last November's election results in all 50 states between this weekend and January 20.

"We very much hope that there will be no violence, either before or during the inauguration on the 20th," Dujarric said.

"People who have disagreements (should) go through established constitutional processes," he added.