Newton (United States) (AFP) - Donald Trump hit the campaign trail Saturday in the first-in-the-nation presidential nominating state of Iowa, vowing to win "for the third time" as Americans marked the anniversary of the deadly assault on the US Capitol by a mob of his supporters.

Many watched in horror three years ago on January 6, 2021, as rioters -- egged on by the ex-president and fueled by his false claims of voter fraud -- stormed the seat of US democracy in a bid to halt the transfer of power.

In a rambling, two-hour speech Saturday to supporters in Newton, Iowa, Trump did not delve into the events of that day, but described those jailed over their roles in the assault as "hostages." He has said that if elected, he will pardon many.

Trump mocked President Joe Biden, his putative rival in November's election.

He said Biden has overseen economic decline and invited chaos at the nation's borders, while failing to stop Russia's invasion of Ukraine.

"I would've absolutely stopped Putin," he said.

Trump warned of World War III if Biden is re-elected, adding, "This is our last chance to save America."

Never having given up on the fiction that he won the 2020 election, Trump declared that in November he will win "for the third time."

The runaway leader in the race for the 2024 Republican presidential nomination, Trump was impeached for inciting insurrection and faces multiple felony charges over his conduct leading up to and during the violence.

In an evening appearance at a middle school in the town of Clinton, Trump gave another meandering speech in which he attacked Biden as too old to govern, incompetent and leading the United States to ruin with overrun open borders.

"We are a failing nation," Trump said in the hour-long address.

"We're going to bring it back from hell," he added.

Biden, who offered blistering criticism of Trump in a speech Friday, has no public events planned this weekend, the White House said.

Trump leads rivals Nikki Haley and Ron DeSantis by more than 30 points in Iowa, which stages its Republican nominating contest -- known as a "caucus" -- on January 15, kicking off the 2024 primary season.

Trump has described January 6 as "a beautiful day" and has made the "great patriots" and "hostages" imprisoned over the riot a cause celebre.

The false claim that Democratic election theft led to January 6 has become orthodoxy among many Republicans, with hard-liners in Congress promoting the fantasy that the chaos at the Capitol was a "false flag" operation by federal agents.

A Washington Post/University of Maryland poll released Thursday found that 44 percent of Trump voters believe the FBI organized and encouraged the riot. 

But polls also show that Democrats and independents hold strongly negative views of the riot and the rioters, and of Trump's role in encouraging them.

"We will never forget the horrific events of January 6, 2021," Democratic House Minority Leader Hakeem Jeffries said in a statement Saturday, adding that those responsible "must be held accountable, because in this country no one is above the law."

Vice President Kamala Harris posted on social media that a victory by those "who seek to dismantle our democracy" would bring violence and chaos.

Threat to democracy

The House, controlled at the time by the Democrats, impeached Trump for inciting the violence, which was linked to the deaths of five police officers and several rioters, although he was acquitted by allies in the Senate and denies all wrongdoing.

A later congressional investigation concluded that the violence was the culmination of a criminal conspiracy led by Trump to subvert the election. The ex-president is facing multiple federal and state felony charges related to the events.

MSNBC on Saturday released chilling new video footage from January 6 showing two Republican lawmakers speaking with Capitol rioters who scream at and taunt them through the broken windows of the House chamber doors. Capitol officers point guns at the mob trying to breach the floor.

Democrats plan to make the tycoon's conduct on January 6 a key campaign issue, pointing to the 450-plus Trump supporters jailed over allegations ranging from seditious conspiracy to trespassing and assaulting police. 

In his speech Friday in Pennsylvania, Biden framed the election as a test of the robustness of the republic and he highlighted the Capitol riot as a demonstration of Trump's threat to democracy.

And he accused his predecessor of echoing Nazis with his rhetoric on immigration, accusing him of being willing to "sacrifice our democracy" to regain power.