President Barack Obama has said he is heartened by Donald Trump's call for unity after his victory adding "we are now all rooting for his success in uniting and leading the country".
Mr Obama spoke to reporters in the Rose Garden of the White House in a post-election ritual meant to signal the peaceful transition of power from one president to the next.
He vowed to do all he could to ensure a smooth transition and tried to buck up Democrats still reeling with disappointment and shock.
"We all want what's best for this country," Mr Obama said, noting he was encouraged by Mr Trump's election night remarks urging reconciliation after an especially bitter and long contest.
He spoke just moments after Hillary Clinton formally conceded to Mr Trump with a similar, though more emotional, appeal to give Mr Trump a chance to succeed as president.
The remarks were striking after a campaign in which the Democrats declared Mr Trump was unfit to serve and told voters the future of democracy was riding on their choice.
An extraordinarily large number of Obama aides and advisers - more than a hundred in all - gathered to hear his statement, including stenographers, low-level aides and White House Counsel Neil Eggleston.
The White House said Mr Obama and Mr Trump are due to meet on Thursday to discuss the handover of power and ongoing planning for the transition.
Mr Obama called the Republican in the early hours of the morning on Wednesday to congratulate him on his victory, which marked a forceful rebuke by voters to the president's eight years in office.
For Mr Obama, handing over the White House to Mr Trump is a devastating blow to his legacy and to his hopes for leaving a lasting imprint on the nation's policies.
Mr Trump has vowed to rip up much of what Mr Obama accomplished, including his signature health care law, the Iran nuclear deal and a painstakingly negotiated trade deal with Asia.
With Republican control of both chambers of Congress, he will be well positioned to make good on that promises.
Mr Obama also called Mrs Clinton after it became clear she had lost the race. The White House said Mr Obama had "expressed admiration for the strong campaign she waged throughout the country".
It was unclear how substantive Mr Obama's call was with Mr Trump, or how long it lasted, although the White House noted that Mr Obama placed the call from his residence in the White House, rather than from the West Wing.
Mr Trump's campaign manager, Kellyanne Conway, described it as a "warm conversation" and a "gracious exchange". She said Mr Trump had missed the president's original call as Mr Trump was speaking to supporters in New York, then called him back after leaving the stage.
Like Mrs Clinton and other Democrats, Mr Obama did not appear to see Mr Trump's victory coming. As he campaigned vigorously for Mrs Clinton in the race's final days, Mr Obama said he was confident that if Americans showed up to vote, they would choose against electing the billionaire former reality TV star with no formal government experience.
He had also warned supporters in apocalyptic terms that "the fate of the republic" rested on Mrs Clinton defeating Mr Trump on election day.