Mr Obama spoke to reporters in the Rose Garden of the White House in a post-election ritual.
Conceding Hillary Clinton's staggering defeat, the outgoing US President Barack Obama urged the nation Wednesday to join him in rooting for President-elect Donald Trump's success. He said he was heartened by Mr Trump's election night call for unity and hoped it wouldn't fade.
Mr Obama, in a post-election ritual meant to signal the peaceful transition of power, vowed to do all he could to ensure Mr Trump would be well-positioned to run the country. He said he'd congratulated Mr Trump by phone and invited him to sit down together at the White House.
"We all want what's best for this country," Mr Obama said.
Standing in the Rose Garden, with Vice President Joe Biden at his side, Mr Obama spoke to more than a hundred of his White House staffers, who stood silently, dazed, some crying, before breaking out into a prolonged round of applause that continued long after Mr Obama returned to the Oval Office.
Mr Obama's conciliatory reaction to the election marked an attempt to buck up Democrats reeling with disappointment, shock and uncertainty about the future. He said he'd told his staff to "keep their heads up" and be proud of the "remarkable work" they'd done.
Left unsaid was that Mr Trump has vowed to aggressively undo most of what Mr Obama has accomplished, leaving Mr Obama's supporters fearful that the last eight years may have been in vain.
But the president, standing in front of the Oval Office, downplayed the notion that Mr Trump's presidency would mean an about-face for the nation. He said the US has a tendency to "zig and zag" rather than move in a straight line, and he added, "That's OK."
"That's the way politics works sometimes," the outgoing President said. "We try really hard to persuade people that we're right and then people vote. And then if we lose, we learn from our mistakes, we do some reflection, we lick our wounds, we brush ourselves off, we get back in the arena, we go at it. We try even harder the next time."
Mr Obama spoke just moments after Ms 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.
The White House said Mr Obama and Mr Trump are expected to meet 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 Wednesday to congratulate him on his stunning victory, which marked a forceful rebuke by voters to Mr Obama's eight years in office.
With Republican control of both chambers of Congress, Mr Trump will be well positioned to make good on that promises.
Mr Obama called Ms Clinton after it became clear she'd lost the race. In his Rose Garden remarks, he paid tribute to her historic candidacy and said, "I could not be prouder of her."
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 Ms Clinton and other Democrats, Mr Obama didn't appear to see Trump's victory coming. As he campaigned vigorously for Ms Clinton in the race's final days, Mr Obama said he was confident that if Americans showed up to vote, they'd 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 Ms Clinton defeating Mr Trump on Election Day.