President Donald Trump delivered an extensive denunciation of special counsel Robert Mueller’s investigation during a highly unusual appearance in the White House Rose Garden on Wednesday, announcing that he would not work with congressional Democrats as long as they persist in investigating him.

“This whole thing was a take-down attempt of the president of the United States,” Trump said, slamming House Speaker Nancy Pelosi's comment earlier that he was “engaged in a cover-up.”

"I don't do cover-ups," the president said.

Just before he appeared in the Rose Garden, Trump had stormed out of an infrastructure meeting with Democratic leaders, including Pelosi and Senate Minority Leader Chuck Schumer, Democratic sources with knowledge of the meeting said.

"I knew the president was not serious about infrastructure and would find a way out," Pelosi quipped as the president stormed out, according to a Democratic aide.

Underscoring the bitterness between the White House and top Democrats, two sources in the room confirm to NBC News that after Trump left the meeting, White House counselor Kellyanne Conway asked Pelosi a question. It was, according to a White House source in the room, "Respectfully, Madam Speaker, do you have a direct response to the president?"

Pelosi responded: "I don't talk to staff. I talk directly to the President."

Conway replied, sarcastically: "That's very pro-woman of you."

A Democratic aide disputed aspects of that account, insisting the Speaker never said she doesn't talk to staff.

Two Democratic sources with knowledge of the meeting told NBC News that Trump arrived late to the meeting and expressed dismay at Pelosi's "cover-up" comments, calling the remarks inconsiderate. Trump then said, according to the sources, Democrats would need to complete their various investigations before a deal on infrastructure or any other topic would be considered.

Trump said he had intended to sit down with Democratic leaders to discuss the $2 trillion infrastructure plan they had agreed to pursue last month, but that he cut the meeting short.

"I walked into the room and I told Senator Schumer and House Speaker Pelosi, 'I want to do infrastructure, I want to do more than you want to do it,'" Trump said. "'But, you know what? You can't do it under these conditions, get these phony investigations over with.'"

The president, in calls with allies and friends outside the White House, has increasingly been "harping on" how he believes Democrats' unity appears to be unraveling. Trump sees a shift from the first two years of his administration, when he privately and publicly grumbled about his party's lack of unity.

There's a sense that impeachment could embolden the president politically, with some allies pointing to former president Bill Clinton’s rise in approval ratings after congressional Republicans moved to impeach him in the late '90s. And others believe impeachment could allow Democrats to the be the president's political foil on the campaign trial.

Back on Capitol Hill, Pelosi, flanked by Schumer and other top Democrats in Congress, said Democrats had gone to the White House in the "spirit of bipartisanship to find common ground with the president," but that his behavior was not "really respectful."

"For some reason, maybe it was lack of confidence on his part, he couldn’t match the greatness of the challenge," she said during an impromptu news conference.

“I pray for the president of the United States and I pray for the United States of America," she added.

“To watch what happened at the White House would make your jaw drop,” Schumer told reporters.

“It's clear this was not a spontaneous move on the president's part,” he said, pointing out that immediately after Trump left the meeting with Democrats, he went out to the Rose Garden that had signs prepared.

Trump spoke at a lectern with a sign in front of it that read “no collusion,” “no obstruction” and cited a $35 million cost of Mueller's probe into Russian election interference and Trump. Two administration sources said the "no collusion" poster pasted on to the president’s podium had been created a while ago.

While Mueller’s investigation didn't establish that members of the Trump campaign conspired or coordinated with the Russian government, it did establish that Russia interfered in the 2016 election, that it did so to help Trump, and that the Trump campaign expected it would benefit from the interference. Mueller's report also detailed numerous attempts by Trump to disrupt the inquiry, though Mueller did not come to a conclusion on whether Trump obstructed justice.

“Accordingly, while this report does not conclude that the President committed a crime, it also does not exonerate him,” Mueller wrote. Attorney General William Barr cleared Trump of obstruction of justice.

The probe cost roughly $25 million, according to the Department of Justice. However, as part of his plea deal with Mueller’s team, Trump’s former campaign chairman Paul Manafort forfeited a host of assets, including New York real estate properties worth an estimated $21.7 million, among other valuables. Manafort was convicted and pleaded guilty in 2018 to multiple charges of fraud, tax evasion and conspiracy and sentenced to a total of 7.5 years in prison.

During his news conference, Trump warned that Democrats could be setting a dangerous precedent and referenced what he called the "I-word" — impeachment, discussions of which have been surging among House Democrats in recent days in light of the Trump administration's refusal to comply with oversight requests, including subpoenas for testimony and documents related to Mueller's report.

"Whether or not they carry the big I-word out, I can't imagine that, but they will do whatever they have to do. There is a danger here," Trump said. "If someday a Democrat becomes president, and you have a Republican House, they can impeach him for any reason — or her, any reason. We can't allow that to happen."

Just over 20 years ago — in 1998 — a Republican House did impeach a Democratic president, Bill Clinton, in the Monica Lewinsky sex scandal.