President Barack Obama is hosting his successor Donald Trump at the White House for what could prove to be awkward transition talks.
The Republican president-elect had during his campaigned questioned President Obama’s US citizenship and vowed to dismantle his legacy.
During the campaign, Obama called Trump “uniquely unqualified”, but now says he is “rooting” for him after his shock defeat of Hillary Clinton.
Thousands have taken to the streets of major US cities denouncing Trump.
White House spokesman, Josh Earnest has insisted that President Obama is sincere about ensuring a smooth handover when he meets Trump, though he added: “I’m not saying it’s going to be an easy meeting.”
Trump flew from New York on his private jet and landed at Reagan National Airport, just outside the nation’s capital.
The president-elect broke from protocol and barred journalists from travelling with him to cover his first meeting with Obama.
The two men are expected to appear together for the cameras in the Oval Office after a behind-closed-doors meeting.
The president-elect is being accompanied by his wife, Melania, who is also expected to hold a meeting with First Lady Michelle Obama.
Obama, who congratulated his successor in a phone call in the early hours of Wednesday, said it was “no secret” that he and Trump had pretty significant differences.
But the Democratic president – who had campaigned against Trump – urged all Americans to accept the result of the presidential election.
“We are now all rooting for his success in uniting and leading the country,” he said.
Trumps opponent in the election, Hilary Clinton, also told supporters that the president-elect must be given a “chance to lead”.
Despite the pleas for unity, protesters gathered across the country on Wednesday, Many chanting: “Not my president.”
Obama and Trump have a history of mutual hostility.
Trump had questioned the legitimacy of Obama’s presidency through the “birther” movement, which falsely claimed the Hawaii-born commander-in-chief was actually born outside the US.
The businessman also called Obama “the worst president in the history of the United States”.
With the Republicans now holding a majority in both chambers of the US Congress, Trump can more easily target key Obama initiatives such as his healthcare reforms.
Vice-President-elect Mike Pence, a favourite among social conservatives, is also meeting behind closed doors on Thursday with Vice-President Joe Biden, one of the Democratic party’s most popular figures.
Trump is already setting up meetings with heads of governments ahead of his January inauguration as the nation’s 45th US president.
The office of British Prime Minister Theresa May said on Thursday that the president-elect had invited her in a phone call to visit him “as soon as possible”.