Biden blames Trump's 'web of lies' for US Capitol attack in one-year anniversary speech

President Joe Biden on Thursday accused his predecessor Donald Trump of spreading a "web of lies" to undermine US democracy in a speech on the anniversary of the deadly Capitol attack by Trump supporters who tried to undo his 2020 election defeat.

Speaking at the white-domed building where rioters smashed windows, assaulted police and sent lawmakers fleeing for their lives on 6 January, 2021, Biden said Trump's false claims that the election was stolen from him through widespread voting fraud could unravel the rule of law and subvert future elections.

"We must be absolutely clear about what is true and what is a lie. Here's the truth: A former president of the United States of America has created and spread a web of lies about the 2020 election. He's done so because he values power over principle," Biden said. "He can't accept he lost."

Biden never actually uttered his predecessor's name during the 25-minute speech, telling reporters afterward he was trying to focus on the threats to America's political system instead of Trump himself.

The tone, including a poke at Trump's "bruised ego," was a departure for Biden, who has focused during most of his first year in office on pursuing his own agenda.

Trump's behaviour over the past year, like his conduct in office, has been norm-shattering. Unlike other former US presidents denied re-election, Trump has refused to accept the verdict of the voters and pressured fellow Republicans to somehow overturn the results, without success.

His false claims have provided cover for Republicans at the state level to pass new restrictions on voting that they have said are needed to fight fraud. Research shows such fraud is extremely rare in US elections.

Biden's fellow Democrats, a few Republicans and many independent experts have said Trump's continued denials could make it less likely that future US transfers of power will be peaceful - especially those involving closer margins than the 2020 election that Biden won by 7 million votes nationwide.

"The former president and his supporters have decided the only way for them to win is to suppress your vote and subvert our elections," Biden said.

In remarks delivered before Biden spoke, Vice President Kamala Harris also cast a spotlight on Trump supporters' efforts to subvert democracy, calling on Congress to pass voting rights legislation and on Americans to participate.

"We cannot let our future be decided by those bent on silencing our voices, overturning our votes and peddling lies and misinformation by some radical faction that may be newly resurgent but whose roots run old," Harris said. "The fragility of democracy is this: that if we are not vigilant, if we do not defend it, democracy simply will not stand; it will falter and fail."

The speech illustrated that Biden and other Democrats remain wary of Trump's political staying power. In the riot's immediate aftermath, even some Republicans thought his grip on their party had been shaken, but since then Trump has only tightened it.

There are 10 months to go until America's next federal election, with Republicans favoured to retake a majority in at least one of the two chambers of Congress. That could cripple Biden's ability to advance policy and set the stage for two years of legislative gridlock before a potential 2024 Biden-Trump rematch.

According to Reuters/Ipsos polling, 55 percent of Republican voters believe Trump's false claims, which were rejected by dozens of courts, state election departments and members of his own administration.

'Divide America'

Trump issued two statements in rapid succession after his successor's remarks, repeating his false election claims and saying that Biden "used my name today to try to further divide America".

Four people died in the hours-long chaos after Trump urged supporters to march to the Capitol and "fight like hell." One police officer died on that day after battling rioters and four later died by suicide. Around 140 police officers were injured. US prosecutors have brought criminal charges against at least 725 people linked to the riot.

Biden's remarks began a series of events that will also feature House of Representatives Speaker Nancy Pelosi and other legislators, mostly Democrats. Many Senate Republicans planned to be out of town for former Senator Johnny Isakson's funeral.

Trump remains highly popular among Republican voters and is actively shaping the field of Republican candidates for the 8 November congressional elections. Public filings show Trump has stockpiled at least $US98 million ($NZ145m) in fundraising accounts.

Most Republican officeholders have remained loyal to Trump, and some have sought to play down the riot. Biden said it was hypocritical for them to question the presidential election's outcome while accepting Republican victories in congressional and state-level races that day.

Any Republicans who have called for accountability including Representatives Liz Cheney and Adam Kinzinger have been shunned by their colleagues.

"As the American people, particularly as Republicans, I think we're almost in a worse position than we were the day after January 6," Kinzinger said.

The two are the only Republican members of a House committee investigating the riot, which in recent weeks has unearthed records showing Trump allies urging him to call off the rioters as the attack was unfolding. Biden on Thursday described the image of Trump "sitting in the private dining roof off the Oval Office in the White House, watching it all on television and doing nothing for hours".

Republicans accused Democrats of exploiting the anniversary for partisan gain.

"It is especially jaw-dropping to hear some Senate Democrats invoke the mob's attempt to disrupt our country's norms, rules, and institutions as a justification to discard our norms, rules and institutions themselves," Senate Republican Leader Mitch McConnell said.

-Reuters