The presumptive Republican nominee in November's presidential election delivered a message of unity, promising to "work out" any lingering differences within the party.

Later in the day, the former president met with an association of 200 corporate leaders.

Nancy Pelosi, the former Democratic House Speaker, said in a statement that Trump was the "instigator of an insurrection... returning to the scene of the crime".

The visit comes a fortnight after Trump's criminal conviction for falsifying business records in his hush-money trial in New York.

He arrived at a Republican office building near the US Capitol building on Thursday morning, passing a small crowd of protesters holding signs with slogans including "failed coup" and "Democracy Forever, Trump Never".

In a brief news conference early on Thursday afternoon, Trump said there was "great unity" in the party, and vowed to stand by fellow Republicans, even those he disagreed with.

"I'm with every one of you. I'll be with you always," he said. "If [a relationship] wasn't fantastic, it gets worked out.

"We have one thing in mind, and that's making our county great again."

Trump did not take questions, but waved and gave a thumbs up at a small group of supporters shouting "I love you".

"Thank you," he mouthed in response.

Following a meeting between Trump and House Republicans earlier in the day, House Speaker Mike Johnson said the former president "brought an extraordinary amount of energy and enthusiasm this morning".

"That is what we're seeing in the party throughout the country," Mr Johnson said. "We believe we are going to win back the White House, and the Senate, and grow the House majority."

Matt Gaetz, a Florida Republican, described Trump's meeting with House Republicans as a "pep-rally environment" for the former president.

Marjorie Taylor Greene, a Georgia Republican, told reporters she saw nothing but "overwhelming support for Trump" among the party rank-and-file.

"I am glad to see Republicans here in Washington rallying around President Trump and his candidacy as president," she said.

Senate minority leader Mitch McConnell, who has been openly critical of Trump in the past, called the visit "really positive".

"He got a lot of standing ovations," Mr McConnell added.

In addition to Mr McConnell, two other Trump critics within the party - Utah Senator Mitt Romney and Louisiana's Bill Cassidy - were at the meeting.

Senator Josh Hawley, a Missouri Republican, described Trump as "extremely gracious" and "warm" to Senate Republicans.

"I guess I've just been here five years, and that's probably the warmest meeting that I have been in with senators and Trump," he told reporters.

Mr Hawley said that Trump spoke about abortion "quite a lot" at the meeting, where he reiterated his stance that voters should be the ones to decide on the issue.

At the earlier meeting with House Republicans, Trump reportedly described Milwaukee as "horrible", a month before the Wisconsin city is due to host the Republican National Convention.

That prompted his spokesman to clarify that he was referencing crime in the city rather than the city itself.

Milwaukee broke its homicide record for three years in a row from 2020-22, though the city's police department statistics show that violent crime, including murder and rape, has fallen significantly over the last two years.

Several lawmakers from the Wisconsin delegation claimed Trump's comments about the city were made in reference to the upcoming election.

But Wisconsin Rep Derrick Van Orden, a Republican, argued Trump's comments about the city were focused on crime.

"You're focusing on a two-second comment that's factually correct by the former president of the United States," Mr Van Orden told reporters on Capitol Hill.

Before the visit, Politico reported that Trump called Mr Johnson to urge him to help reverse his 31 May conviction on 34 counts of falsifying documents in New York.

"We have to overturn this," Trump reportedly said in an expletive-laden call.

New York Republican representative Marcus Molinaro told CBS, the BBC's US partner, that Trump made no mention of the conviction when meeting with House Republicans.

More than three years ago, Trump urged supporters to "fight like hell" but also to march "peacefully" hours before a mob stormed the US Capitol on 6 January 2021 as lawmakers certified Joe Biden's election victory.

Mrs Pelosi said in her statement: "Donald Trump comes to Capitol Hill today with the same mission of dismantling our democracy.

"Make no mistake - Trump has already cemented his legacy of shame in our hallowed halls."