The new president and first lady Jill Biden walked through a military cordon lining the White House driveway to complete an abbreviated inaugural afternoon unlike any Washington has seen.

In his inauguration speech, Biden offered a message of unity and restoration to a deeply divided country reeling from a battered economy and a raging coronavirus pandemic that has killed more than 400,000 Americans.

Standing on the steps of the US Capitol two weeks after a mob of Donald Trump’s supporters stormed the building, Biden called for a return to civic decency.

“To overcome these challenges, to restore the soul and secure the future of America, requires so much more than words. It requires the most elusive of all things in a democracy: unity,” the Democrat said after taking the oath of office.

“We must end this uncivil war that pits red against blue, rural versus urban, conservative versus liberal. We can do this. if we open our souls instead of hardening our hearts.”

The themes of Biden’s 21-minute speech mirrored those at the centre of his presidential campaign, when he portrayed himself as an empathetic alternative to the divisive Trump, a Republican.

The inauguration itself served as a stark reminder of both the tumult that defined the Trump era as well as the pandemic that still threatens the country.

Amid warnings of possible renewed violence, thousands of armed National Guard troops circled the Capitol in an unprecedented show of force.

The National Mall, typically packed with throngs of supporters, was instead filled with nearly 200,000 US flags.

Those attending, including former presidents Barack Obama, George W. Bush and Bill Clinton, wore masks and sat several feet apart.

Biden’s running mate, Kamala Harris, the daughter of immigrants from Jamaica and India, became the first black person, first woman and first Asian American to serve as vice president after she was sworn in by US Supreme Court Justice Sonia Sotomayor, the court’s first Latina member.

The president spoke forcefully about the Capitol siege when Trump backers breached the building. But Biden never mentioned his predecessor by name.

The violence prompted the Democratic-controlled US House of Representatives to impeach Trump last week for an unprecedented second time, accusing him of incitement after he exhorted his backers to march on the building to press false claims of election fraud.

“Here we stand, just days after a riotous mob thought they could use violence to silence the will of the people, to stop the work on our democracy, to drive us from this sacred ground,” Biden said.

“It will never happen. Not today, not tomorrow, not ever.”

Trump flouted one last convention on his way out of the White House when he refused to meet with Biden or attend his successor’s inauguration, breaking with a political tradition seen as affirming the peaceful transfer of power.

Trump, who never conceded the November 3 election, did not mention Biden by name in his final remarks as president on Wednesday morning, when he touted his administration’s record.

He then boarded Air Force One for the last time and flew to his Mar-a-Lago retreat in Florida.

Biden takes office at a time of deep national unease, with the country facing what his advisers have described as four compounding crises: the pandemic, the economic downturn, climate change and racial inequality.

He has promised immediate action, including a raft of executive orders on his first day in office.

After a bitter campaign marked by Trump’s baseless allegations of election fraud, Biden struck a conciliatory tone rarely heard from Trump, asking Americans who did not vote for him to give him a chance.

“I pledge this to you: I will be a president for all Americans,” he said.

“And I promise you I will fight as hard for those who did not support me as for those who did.”

Although his remarks were directed primarily at domestic problems, Biden also delivered a message to the rest of the world. He promised to repair alliances frayed by Trump and act as a strong partner for peace, progress and security.

World leaders issued congratulatory statements, with several US allies expressing relief at Biden’s inauguration after Trump’s unpredictable tenure.

Biden will waste little time turning the page on the Trump era, aides said, signing 15 executive actions on issues ranging from the COVID-19 pandemic to the economy to climate change.

Less than an hour after his swearing-in, Biden posted his first official tweet from the @POTUS account after Twitter transferred it from Donald Trump’s control.

“There is no time to waste when it comes to tackling the crises we face,” Biden said in the post at 12.36 pm eastern time in the US on Wednesday.

“That’s why today, I am heading to the Oval Office to get right to work delivering bold action and immediate relief for American families.”

Wall Street stocks closed at a record high after the inauguration.

Biden will attempt to jump-start the federal government’s response to the coronavirus pandemic with a string of immediate executive orders after his inauguration to lead a country reeling from its worst public health crisis in more than a century.

World leaders expressed hope that Biden would right the world’s largest democracy after they watched rioters storm the US Capitol, shaking the faith of those fighting for democracy in their own countries.

Pope Francis urged Biden to help foster reconciliation in the US and build up a society “marked by authentic justice and freedom” and looking out especially for the poor.

Australian Prime Miniser Scott Morrison joined other world leaders in congratulating the 46th US president and his deputy Kamala Harris on their inauguration.

“The Australia-US Alliance has never been more important,” the Prime Minister said on Thursday.

“I wish you both every success for your time in office and look forward to working closely with your new administration.”

Opposition Leader Anthony Albanese also offered his congratulations as Biden entered the White House.

“We have seen a mishandling of the pandemic in the United States and Joe Biden will have a difficult task ahead,” Albanese said.

“The rise of Kamala Harris to the vice presidency – a woman of colour – reflects modern America, as does Joe Biden’s cabinet,” he said.

Biden said that his swearing-in marks a day of “history and hope”.

He plans to bring the US back to the fight to slow global warming in one of his first official acts by rejoining the Paris Agreement.

Biden says he will immediately launch a series of climate-friendly efforts that would transform how Americans drive and get their power.

“A cry for survival comes from the planet itself,” Biden said in his inaugural address.

“A cry that can’t be any more desperate or any more clear now.”

Israeli Prime Minister Benjamin Netanyahu, who formed close ties with Trump, noted a “warm personal friendship” with Biden.

Former Colombian president and Nobel Peace Prize winner Juan Manuel Santos said Biden “understands the importance of co-operation among nations”.

“If we don’t co-operate – all nations – to fight climate change, then we will all perish. It’s as simple as that,” Santos said.

French President Emmanuel Macron also noted the urgency of addressing climate change after Trump withdrew the US from the Paris climate accord, a move Biden was to reverse in the first hours of his presidency.

“We will be stronger to face the challenges of our time. Stronger to build our future. Stronger to protect our planet,” he wrote on Twitter.

“Welcome back to the Paris Agreement!”

To @JoeBiden and @KamalaHarris.
Best wishes on this most significant day for the American people!
We are together.
We will be stronger to face the challenges of our time. Stronger to build our future. Stronger to protect our planet. Welcome back to the Paris Agreement!

— Emmanuel Macron (@EmmanuelMacron) January 20, 2021

British Prime Minister Boris Johnson said he looked forward to working with Biden “on our shared priorities”.

“From tackling climate change, building back better from the pandemic and strengthening our transatlantic security,” he said.

Elsewhere in Europe, close US allies finally saw a chance to come in out of the cold after strained security and economic relationships with the Trump administration.

-AAP