U.S. President-elect Donald Trump makes his first appearance at the White House on Thursday, after his stunning upset over Hillary Clinton in Tuesday’s presidential election.

The Republican victor will meet with President Barack Obama to begin the gradual transfer of power so that Trump is ready to be sworn in January 20.

Obama campaigned hard for Clinton’s election and acknowledged Wednesday that losing is tough.

“It is no secret that the president-elect and I have some pretty significant differences,” Obama said. “But remember, eight years ago, President Bush and I had some pretty significant differences. But President Bush’s team could not have been more professional or more gracious in making sure we had a smooth transition.”

WATCH: Obama confident of peaceful transition of power

Obama said he is rooting for Trump’s success and has ordered the White House team “to work as hard as we can to make sure that this is a successful transition for the president-elect.”

Obama called the peaceful transition of power one of the hallmarks of U.S. democracy.

Just before Obama’s White house appearance, Democratic candidate Hillary Clinton made her first public appearance since she telephoned her concession to Trump.

WATCH: Hillary Clinton on ‘painful’ election loss

Surrounded by her family and her running mate, Tim Kaine, in New York, the usually cool Clinton choked back tears as she bade farewell to her staff and said losing her chance to be president “is painful and it will be for a long time.”

“This is not the outcome we wanted or we worked hard for … but I feel gratitude for this wonderful campaign that we built together,” Clinton told members of the crowd, many of whom were weeping. “I know how disappointed you feel because I feel it, too, and so do the tens of millions of Americans who invested their hopes and dreams in this effort.”

Clinton told her fellow Democrats that they owe Trump “an open mind and a chance to lead,” and she wished him a successful administration.

Clinton actually beat Trump in the popular vote by more than 206,000 votes. But under the U.S. system, it is the Electoral College that decides the presidency, and with 270 electoral votes needed to win, Trump won 279 votes to Clinton’s 228.

Pre-election day polls were giving Clinton a 2- to 3-point edge over Trump.

Republican President-elect Donald Trump delivers his acceptance speech during his election night event at the New York Hilton Midtown in New York City, Nov. 9, 2016.

But Trump prided himself on being a non-politician and a Washington outsider. He painted Clinton as someone who is an expert at manipulating the political system for personal gain, while ordinary Americans watch their jobs disappear and economic opportunities dry up.

Obama has warned that a Trump presidency would undo his eight years of progress in bringing the country out of recession and two wars.

But Trump has said a Clinton administration would be nothing but a third Obama term, and promised to bring a change from the status quo that he said voters demanded.

In Photos: Republicans, Democrats React to Vote