US President Joe Biden has accused his predecessor Donald Trump and his supporters of undermining democracy, ahead of next week's midterm elections.

"Make no mistake, democracy is on the ballot for all of us," Mr Biden, a Democrat, said, referring to threats by some Republicans candidates to refuse to accept the outcome should they lose.

Republicans hit back, saying Mr Biden was seeking to "divide and deflect".

Control of both chambers of Congress is at stake in the 8 November vote.

Most forecasts suggest Republicans will win control of the House of Representatives, while the Senate could go either way. The political make-up of the chambers has a huge bearing on how easily Mr Biden and his party can get new laws passed.

In his nationally televised remarks on Wednesday night, Mr Biden accused former President Trump of fuelling anger, hate, vitriol and violence by refusing to accept the results of the 2020 presidential election.

Referring to the recent attack on the husband of the Democrat House speaker Nancy Pelosi, he said violence was the consequence of lies born out of conspiracy and malice.

The US government last week distributed a bulletin to law enforcement agencies warning of a "heightened threat" of domestic violent extremism ahead of the mid-terms, adding that candidates and election workers could be targeted by individuals with "ideological grievances".

Mr Biden's speech was delivered at Washington DC's Union Station, a few streets from where Trump supporters stormed the US Capitol last year in an attempt to overturn the results of the 2020 election.

"As I stand here today, there are candidates running for every level of office in America - for governor, for Congress, for attorney general, for secretary of state - who won't commit to accepting the results of the elections they're in," he said.

Republicans said President Biden was trying to distract Americans from his low approval ratings - and from US inflation.

House Republican minority leader Kevin McCarthy, who would become speaker of the lower chamber of Congress should his party win control next week, tweeted: "President Biden is trying to divide and deflect at a time when America needs to unite - because he can't talk about his policies that have driven up the cost of living.

"The American people aren't buying it."

A Reuters/Ipsos opinion poll this week found that half of Americans believe voter fraud is a widespread problem, even though such cases are extremely rare.

According to the BBC's US partner CBS, out of 595 Republicans running for state-wide office, just over half - 306 - have raised doubts about the 2020 presidential election.