Donald Trump has retweeted three inflammatory videos from a British far-right group.
The first tweet from Jayda Fransen, the deputy leader of Britain First, claims to show a Muslim migrant attacking a man on crutches.
This was followed by two more videos of people Ms Fransen claims to be Muslim.
Britain First was founded in 2011 by former members of the far-right British National Party (BNP).
The group has grabbed attention on social media with controversial posts about what they deem “the Islamification of the UK”.
It has put up members to run in European elections and by-elections on anti-immigration and anti-abortion policies, but has yet to secure any seats.
It also contested the most recent London mayoral election, receiving 1.2% of the vote.
The original video was shared by US conservative commentator Ann Coulter who Mr Trump follows.
Ms Fransen has more than 52,000 followers on Twitter.
She responded enthusiastically to Mr Trump sharing her tweets. She posted on her account: “Donald Trump himself has retweeted these videos and has around 44 million followers!”
“God bless you Trump! God bless America!” she added. The message was also shared on Britain First’s Twitter account.
Earlier this month, Ms Fransen was charged with using “threatening, abusive or insulting words or behaviour” during speeches she made in Belfast.
She will appear at Belfast Magistrates’ Court on Thursday 14 December.
Mr Trump’s decision to retweet the videos met dismay on social media.
Brendan Cox, whose wife, British MP Jo Cox, was murdered by a right-wing extremist who shouted “Britain First” before committing the act, has condemned the action.
TV presenter and journalist Piers Morgan, who has called himself a “friend” of the president, tweeted: “What the hell are you doing?”
“Please STOP this madness & undo your retweets,” he said.
The Muslim Council for Britain called on the UK government to “distance” itself from the comments.
“This is the clearest endorsement yet from the US president of the far-right and their vile anti-Muslim propaganda,” a spokeswoman said.
The issue was raised in the UK parliament, and opposition Labour MP Yvette Cooper called on the government to condemn the actions of Mr Trump.
But House of Commons Speaker John Bercow said it would be wrong to expect the government to immediately respond.