American democracy is under attack: Biden

President Joe Biden warns that threats by some Republican candidates to refuse to accept results from the November 8 elections if they lose is a threat to democracy and he blamed former president Donald Trump for inspiring them.

"Make no mistake, democracy is on the ballot for all of us," Biden said in a speech just days before Americans decide whether Democrats maintain control of both the US Senate and House of Representatives or hand over power to Republicans.

Biden, speaking on Wednesday night at Washington's Union Station not far from Capitol Hill, used the hammer attack on Paul Pelosi, husband of US House Speaker Nancy Pelosi, at their San Francisco home as evidence that democracy is under threat less than two years after the January 6, 2021, attack on the US Capitol.

"The assailant entered the home asking, 'Where's Nancy? Where's Nancy?' Those were the very same words used by the mob when they stormed the US Capitol on January 6," Biden said.

He urged voters to "think long and hard about the moment we are in".

"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.

Biden said election deniers had been inspired by Trump, who is pondering a run for president in 2024 just as Biden works to decide if he wants to seek another four-year term.

Biden said "American democracy is under attack" because Trump would not accept the results of the 2020 election that he lost to Biden.

Biden, who is engaged in a frenzy of campaigning for Democrats in the waning days before next Tuesday's midterm elections, is facing the possibility that Republicans will win control of Congress, which would stymie his agenda.

Most midterm forecasts predict Republicans are almost certain to take control of the House, while the Senate is a toss-up.

Biden said "the fate of the nation" lay with the people, and he closed his speech on an optimistic note.

"My fellow Americans, we'll meet this moment. We just have to remember who we are. We are the United States of America. There is nothing beyond our capacity if we do it together," he said.

Trump's supporters stormed the Capitol on January 6, 2021, in an attempt to stop the official certification of Biden's victory in the November 2020 election.

While reviews by dozens of courts, state authorities and members of Trump's own administration have repudiated his false claims that his election defeat was the result of widespread fraud, he has continued airing them since leaving office.