US President Donald Trump has called for the Proud Boys to "stand down" after he failed to condemn the far-right group during his first election debate with challenger Joe Biden.

When asked during the event in Cleveland if he would instruct the male-only group of neo-fascists to obey the direction of law enforcement, Mr Trump said: "Proud Boys, stand back and stand by. But I'll tell you what, somebody's got to do something about antifa and the left."

The next day he tried to walk back his refusal to condemn the group, who have clashed violently with far-left demonstrators.

"I don't know who Proud Boys are. But whoever they are they have to stand down, let law enforcement do their work," Mr Trump told reporters as he left the White House for a campaign stop in Minnesota.

The president went on call out forces on the other end of the political spectrum and tried to attack Mr Biden, echoing how he blamed "both sides" for the 2017 violence between white supremacists and anti-racist protesters in Charlottesville, Virginia.

He said on Wednesday: "Now antifa is a real problem. The problem is on the left. And Biden refuses to talk about it."

In fact, FBI Director Christopher Wray told a congressional panel last week that it was white supremacists and anti-government extremists who have been responsible for most of the recent deadly attacks by extremist groups in the US.

Proud Boys leaders and supporters took to social media to celebrate the president's comments at the debate, with more than 5,000 of the group's members posting "Stand Back" and "Stand By" above and below the group's logo.

And when Mr Trump was directly asked on Wednesday if he "would welcome white supremacist support," he ignored the question and again stressed the need for "law and order".