Sitting in the Oval Office, in front of a strong fire in the fireplace, the former rivals shook hands before Biden called Trump "Mr. President-elect and former president" and then settled simply on "Donald."

"Congratulations," the Democrat told the Republican. "I look forward to having, like they said, a smooth transition. Welcome. Welcome back."

Trump replied, "Thank you very much," saying that "politics is tough. And it's, in many cases, not a very nice world. But it is a nice world today, and I appreciate it very much."

Except for the opening moments, the meeting was private, with Biden and Trump joined by their chiefs of staff. Trump said the transition between the outgoing and incoming administrations "will be as smooth as it can get and I very much appreciate that, Joe."

Trump, the winner this time, says he's ready to ensure that there is a seamless move between administrations. But when he lost four years ago, it was a very different story: Trump filed scores of lawsuits falsely claiming widespread voter fraud, refused to actively participate in transition work, denied the election results and helped incite a mob that attacked the U.S. Capitol, trying to stop the certification of Biden's victory.

He also didn't invite Biden to the White House, and he refused to attend the inauguration -- the first time that had happened since Andrew Johnson skipped Ulysses S. Grant's swearing-in 155 years ago.

The new, all-smiles scene at the White House -- despite what occurred four years ago -- put in stark relief the remarkable political rebound for Trump, who departed Washington in 2021 as a diminished, politically defeated leader. Today he's preparing to come back to power with the Republicans having taken back the Senate, on the cusp of clinching a House majority and with what he and his GOP allies see as a mandate for governance.

Neither the president-elect nor Biden answered questions shouted by reporters after their brief remarks. At one point, Biden looked at Trump, who moved his head to the side and gave a small shrug, but did not respond.

Trump later told The New York Post that he and Biden discussed two issues on which they have differed sharply, the war in Ukraine and Israel's ongoing war with Hamas in Gaza.

"I asked for his views and he gave them to me," Trump told the paper. "Also, we talked very much about the Middle East, likewise. I wanted to know his views on where we are and what what he thinks. And he gave them to me, he was very gracious."

It was unclear how long the president-elect's mild attitude toward Biden, set to be both his successor and predecessor at the White House, might last. After his 2016 election win, Trump met with President Barack Obama in the Oval Office and called it "a great honor." But he soon was back to heaping insults on Obama.

Trump looked at ease in the Oval Office in Wednesday, unlike eight years ago, when he appeared nervous and subdued when meeting with Obama. The president-elect left the White House after his session with Biden without addressing the large contingent of reporters on the driveway, waiting in case he made an appearance.

First lady Jill Biden greeted Trump upon his arrival and gave him a handwritten letter of congratulations for his wife, Melania, who did not make the trip to Washington. The letter also expressed the first lady's team's readiness to assist with the transition.

As he met with Biden, Trump sent out a fundraising email to supporters saying that he "is inside the White House right now conducting a very important meeting."

Trump had flown from Florida in the morning, joining up with billionaire Elon Musk for a morning session with House Republicans, telling them, "It's nice to win."

He received a standing ovation from GOP lawmakers, many of whom took cellphone videos of Trump, as he ran through their party's victories up and down the ballot.

"I suspect I won't be running again unless you say he's good, we got to figure something else," Trump said to laughter from the lawmakers. The Constitution's 22nd Amendment prevents presidents from running for a third term.

House Speaker Mike Johnson, R-La., said of Trump's arrival, "He is the comeback king."

"We owe him a great debt of gratitude," Johnson said.

Trump's reemergence comes amid Republican congressional leadership elections. He's endorsed Johnson's return to the speaker's office, with the president-elect saying he is with Johnson all the way, according to a person familiar with the remarks but not authorized to publicly discuss the private meeting.

Musk joining Trump on the Washington trip came after the Tesla and SpaceX CEO has been spending much of his time at Mar-a-Lago, Trump's Florida estate, and participating in discussions as the incoming Trump administration prepares to transition from Biden's. Trump has named Musk to a government efficiency advisory role in his incoming administration. Some close to the president-elect and his team now see Musk as the second most influential figure in Trump's immediate orbit, after Susie Wiles, the campaign manager who is Trump's incoming chief of staff.

Biden insists that he'll do everything he can to make the transition to the next Trump administration go smoothly. That's despite having spent more than a year campaigning for reelection and decrying Trump as a threat to democracy and the nation's core values. Biden then bowed out of the race in July and endorsed Vice President Kamala Harris to succeed him.

Traditionally, as the outgoing and incoming presidents meet in the West Wing, the first lady hosts her successor upstairs in the residence, But her office said Melania Trump wasn't attending, saying in a statement that "her husband's return to the Oval Office to commence the transition process is encouraging, and she wishes him great success."

Wednesday's trip was not the first time Trump has returned to the Capitol area since the end of his first term. Congressional Republicans hosted him over the summer.

Trump left Washington Wednesday without visiting his party's senators. While he was in town, they chose Sen. John Thune of South Dakota in a three-way race to replace outgoing GOP leader Mitch McConnell of Kentucky. Trump's allies were pushing GOP senators to vote for Sen. Rick Scott of Florida.

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Associated Press writers Jill Colvin in New York and Farnoush Amiri, Darlene Superville and Kevin Freking contributed to this report.