WASHINGTON — President Obama met Thursday at the White House with Donald Trump, his elected successor and longtime political nemesis, to begin a whirlwind 10-week transition before Trump’s inauguration in January.

The Oval Office meeting marked the first face-to-face conversation between the two men and the opening gambit in a transfer of power that is being watched closely across the globe.

During brief remarks to reporters, Obama referred to Trump as “Mr. President-elect” and sought to reassure the country that a smooth and orderly handoff is his administration’s top priority. Trump, sitting next to him in an armchair under a portrait of George Washington, also struck a magnanimous note and pledged to seek Obama’s counsel in the coming weeks.

“We now are going to want to do everything we can to help you succeed,” Obama said, “because if you succeed, then the country succeeds.”

The private meeting was one of several for Trump in Washington on Thursday. After leaving the White House, he met on Capitol Hill with House Speaker Paul Ryan, R-Wis., and Senate Majority Leader Mitch McConnell, R-Ky.

After a flight on his private jet from New York City, Trump entered the White House through the South Lawn entrance – avoiding news cameras and the president’s staff – and he and Obama met for longer than expected.

Trump noted that the session was expected to last 10 to 15 minutes but went on much longer.

“As far as I’m concerned, it could have lasted a lot longer,” Trump said. “We discussed a lot of different situations, some wonderful and some difficulties. I very much look forward to dealing with the president in the future, including counsel.”

White House press secretary Josh Earnest told reporters after the meeting that the two men did not try to resolve all of their differences, but he said it was “a little less awkward” than reporters might have anticipated. Obama and Trump met privately without any staff in the room.

A large part of the meeting was devoted to a discussion about how to staff and organize the White House.

“That’s complicated business,” Earnest said, noting that presidents have to deal with multiple challenges and crises at the same time. It is “something President Obama has thought about extensively over the past eight years.”

SETTING ASIDE THEIR DIFFERENCES

The two men made an overt effort to put their differences behind them.

“Mr. President, it was a great honor being with you, and I look forward to being with you many, many more times in the future,” Trump said, adding that he thinks Obama is “a very good man.”

Obama said he is encouraged by Trump’s interest in working with him and his administration “around many of the issues that this great country faces.”

“I believe that it is important for all of us, regardless of party and regardless of political preferences, to now come together, work together, to deal with the many challenges that we face,” Obama said.

Michelle Obama and incoming first lady Melania Trump met separately Thursday, sharing tea in the White House residence. Michelle Obama gave Melania Trump a tour of the State Floor and the Truman Balcony, and they discussed raising children in the White House. The Trumps have a 10-year-old son, Barron.

For months, President Obama denounced Trump as “temperamentally unfit” for the White House during a long and brutal campaign. But he said that “we are now all rooting for his success in uniting and leading the country. The peaceful transition of power is one of the hallmarks of our democracy. And over the next few months, we are going to show that to the world.”

Trump and Hillary Clinton already had been receiving national security briefings as the nominees of the two major political parties. The White House said Obama has convened a coordinating council to facilitate a smooth transition, including providing briefings from federal agencies to Trump’s transition team, led by New Jersey Gov. Chris Christie.

Officials from the Trump transition team are starting to set up shop in agencies across the federal government, where they can consult with top Obama officials as they assemble their staffs.

Later at the Capitol, Trump met with Republican leaders and began to lay out their plans, many of which involve reversing course on Obama’s priorities.

“We’re going to lower taxes,” Trump told reporters, with Ryan seated by his side. “We’re going to fix health care and make it affordable and better.” This appeared to be a reference to a plan to lower taxes that heavily benefits top earners, and to the Republican Party’s goal of repealing the Affordable Care Act, Obama’s signature domestic-policy achievement.

Ryan ushered Trump onto the Speaker’s Balcony and gestured toward the Washington skyline and the monuments west of the Capitol. He pointed to an inaugural platform being built on the Capitol grounds, showing Trump where he will be taking the oath of office as president.

McConnell joined Trump and his entourage on a walking tour through part of the building.

LONG HISTORY OF ACRIMONY

At the White House, despite their magnanimity and pledges of cooperation, there were small signs of the simmering tension between Trump and Obama. The White House, for example, did not arrange for the traditional photo op between the current first couple and the incoming one.

There is longstanding bad blood between Trump and Obama, and the presidential campaign made it worse.

During Obama’s first term, Trump led a long public campaign against the legitimacy of his presidency by questioning whether Obama was born in the U.S. Trump’s crusade led the president to release his long-form birth certificate in 2011 in an effort to answer conservatives who asserted the president was not an American.

During the White House Correspondents’ Association dinner that year, Obama lit into Trump, mocking him before a ballroom of 2,000 guests and on live television. During the campaign, Trump promised to repeal the president’s signature health-care law and overturn many of his executive actions. Obama said Trump was not to be trusted with the nation’s nuclear codes and represented an existential threat to democracy.

Obama sought to play down that history after the election, saying in a Rose Garden speech Wednesday that in victory, Trump had set the right tone in trying to heal the nation’s political divisions. Obama has pledged to emulate with Trump’s transition team the close working relationship he enjoyed with President George W. Bush during their transfer of power eight years ago.

As the two leaders met, White House Chief of Staff Denis McDonough gave a tour to Trump’s son-in-law, Jared Kushner, and other aides, notably Dan Scavino, across the edge of the Rose Garden.

The current White House has already begun to transfer an extensive amount of information to the National Archives and Records Administration: So far, it has sent 283 million files.

In an interview Wednesday, White House communications director Jennifer Psaki said the president has talked privately with his staff, as well as publicly, about putting institutional interests ahead of political ones.

Referring to the speeches that Obama delivered upon winning the presidency and at his first inaugural, she said: “He reflects a lot about the cog in the wheel that you are as president. He was taking the baton; he’s handing it off. But I think it’s a recognition that it’s bigger than individual aspirations and it’s bigger than yourself, and bigger than anything that you’ve accomplished. Because we as a country need to be stable, need to have continuity.”

In the wake of protests over Trump’s win, Earnest noted that while the president says the protesters have a right to express their opinions, his message to them is that “we’re Americans and patriots first.”

Ohio Gov. John Kasich, who ran unsuccessfully in the Republican presidential primaries and harshly criticized Trump, was at the White House on Thursday to attend Obama’s ceremony for the National Basketball Association champion Cleveland Cavaliers. Speaking to reporters outside the West Wing, Kasich said he saw people protesting Trump’s election as he entered the White House gates.

“I just want to remind everyone in our country that the office of the presidency needs to be respected,” he said. “Today, I said my prayers on the plane for the success of Donald Trump. And I think, as Americans, we all need to come together.”