Video report by ITV News Washington Correspondent Robert Moore
Joe Biden has kicked off his presidency by issuing a raft of measures undoing the work of his predecessor Donald Trump and indicating a more pro-immigration stance.
Sitting in the Oval Office just hours after his inauguration, a face covering wearing Mr Biden said there was “no time to start like today” while seated behind the Resolute Desk with a pile of executive orders.
The first order Mr Biden signed was related to the coronavirus pandemic, which is to mandate mask wearing on federal property.
He also signed an order re-entering the US into the Paris climate accord.
While his predecessor Donald Trump broke long-standing practice by skipping Mr Biden’s inauguration, he did follow through on one tradition and left behind a letter for the new president.
Mr Biden said Mr Trump “wrote a very generous letter” but added that he would not reveal its contents until he had a chance to speak with his predecessor.
Other executive orders signed by Mr Biden included halting work on a border wall with Mexico, lifting a travel ban on people from several predominantly Muslim countries and reversing plans to exclude people in the country illegally from the 2020 census.
The new commander in chief also ordered his cabinet to work to preserve Deferred Action for Childhood Arrivals, a program known as DACA that has shielded hundreds of thousands of people who came to the US as children from deportation since it was introduced in 2012.
He has also extended temporary legal status to Liberians who fled civil war and the Ebola outbreak to June 2022.
The 78-year-old's most ambitious proposal, which he unveiled on Wednesday, is an immigration bill that would give legal status and a path to citizenship to anyone in the United States before the start of 2021 — an estimated 11 million people — and reduce the time that family members must wait outside the United States before being given permanent residency.
Mr Biden began signing the executive orders soon after entering the White House with his family.
The Bidens entered their new home following a much smaller procession through the streets of Washington.
The cavalcade, which normally draws crowds of thousands, was hugely scaled back due to the coronavirus pandemic and concerns of unrest after riots earlier this month.
Similarly the inauguration ceremony was conducted 'virtually' with fewer guests and tighter security.
As he was sworn in as president, Mr Biden called on Americans to overcome divisions, pleading for an end to this 'uncivil war that that pits red against blue'.
In his first address in office, Mr Biden declared that “without unity, there is no peace” while pledging that he would be honest with the country as it continues to confront difficulties, saying that leaders have an obligation “to defend the truth and defeat the lies.” He asked even those who did not vote for him to give him a chance. He said: “Hear me out as we move forward.”
As he did frequently during the campaign, Mr Biden pledged that he will be a “president for all Americans” and will “fight as hard for those who did not support me as for those who did.” He added: “We must end this uncivil war that pits red against blue.”
Wednesday's Inauguration Day is without the presence of the outgoing president for the first time in 152 years.
ITV News Washington Correspondent Robert Moore reflects on the message of 'unity' in President Biden's speech - but can the new administration achieve it?
And with Washington DC essentially in lockdown, the Presidential Inaugural Committee (PIC) announced virtual Inauguration Day events for Americans to watch after urging people to refrain from attending in person.
Lady Gaga took to the stage to sing the National Anthem ahead of Kamala Harris being sworn in as vice president, breaking historic gender and racial barriers in American politics.
The former US senator from California is also the first black person and the first person of South Asian descent elected to the vice presidency and will become the highest-ranking woman ever to serve in government.
Jennifer Lopez also took to the stage, singing partially in Spanish, just before Joe Biden swore on the Bible to officially become the 46th president.
One of the unexpected stars of the ceremony was Amanda Gorman. At 22, she became the youngest poet to perform at a presidential inauguration.
She finished writing her poem, titled 'The Hill We Climb', after rioters stormed the Capitol building two weeks ago. It reflected the theme of unity throughout the ceremony.
Americans had been told to 'stay home' to prevent further spread of the coronavirus that has claimed more than 400,000 lives in the United States.The ceremony in which presidential power is transferred - a hallowed American democratic tradition - serves as a reminder of the challenges Biden faces.
The inauguration unfolded at a US Capitol battered by an insurrectionist siege just two weeks ago.
Ahead of the Inauguration, Donald Trump departed the White House for the final time as US president, travelling to Florida to greet supporters instead of attending the inauguration.
Trump is the first president in more than a century to skip the inauguration of his successor.He told his supporters: “I will always fight for you. I will be watching. I will be listening and I will tell you that the future of this country has never been better."
Mr Trump did adhere to one tradition and left a note for Mr Biden in the Oval Office, according to the White House, which did not release its contents.
And Mr Trump, in his farewell remarks, hinted at a political return, saying “we will be back in some form.”
Washington Correspondent Robert Moore says that in retrospect the focus of Joe Biden's inauguration could be Kamala Harris
Mr Biden tweeted a touching tribute to his wife, Jill, as the celebrations kicked off. He wrote on
Twitter: "I love you, Jilly, and I couldn’t be more grateful to have you with me on the journey ahead."
ITV News Presenter Tom Bradby looks back on previous US Inaugurations
Prime Minister Boris Johnson immediately congratulated the new president.
He tweeted: "America’s leadership is vital on the issues that matter to us all, from climate change to COVID, and I look forward to working with President Biden."
The Queen also sent a private message to Joe Biden, Buckingham Palace has said.
The details of the message have not been released, but it is likely the head of state sent her good wishes to America’s new leader.
During the Queen’s 68-year reign, there have now been 14 American presidents – from Harry S Truman to Mr Biden. Mr Biden comes to office with a well of empathy and resolve born by personal tragedy as well as a depth of experience forged from more than four decades in Washington. At age 78, he will be the oldest president inaugurated.
He wasted no time in making use of his official @POTUS Twitter account, announcing that he will head to the Oval Office "today" to "get right to work".
Biden's first tweet as president said: "There is no time to waste when it comes to tackling the crises we face.
"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."
With tens of thousands of troops on the streets to provide security, the tense atmosphere evoked the 1861 inauguration of Lincoln, who was secretly transported to Washington to avoid assassins on the eve of the Civil War, or Roosevelt’s inaugural in 1945, when he opted for a small, secure ceremony at the White House in the waning months of World War II. Despite security warnings, Mr Biden declined to move the ceremony indoors and instead addressed a small, socially distant crowd on the West Front of the Capitol. Some of the traditional trappings of the quadrennial ceremony remained in place.
In the evening, in lieu of the traditional glitzy balls that welcome a new president to Washington, Biden will take part in a televised concert that also marks the return of A-list celebrities to the White House.
Mr Biden's first days in office are likely to still be shadowed by his predecessor, with Trump’s second impeachment trial set to start. Mr Biden launched an ambitious first 100 days that includes a push to speed up the distribution of Covid-19 vaccinations to Americans and pass a $1.9 trillion virus relief package.
Watch ITV News' special coverage of the inauguration: