– President Donald Trump directed the acting White House chief of staff to freeze more than $391 million in aid to Ukraine in the days before Trump was scheduled to speak by phone with the new Ukrainian president, two senior administration officials said Monday.

Trump’s directive was communicated to the Pentagon and the State Department, which were told only that the administration was looking at whether the spending was necessary, the officials said.

The revelation that Trump ordered the aid package blocked, which was first reported by the Washington Post, adds a vital new element to the raging debate over pressure being put on Ukraine by Trump to investigate unsubstantiated allegations that former Vice President Joe Biden and his son Hunter Biden had engaged in corrupt activities in dealing with Ukraine.

It came on a day when leading congressional Democrats demanded that the Trump administration turn over documentation about the allegations against the president, and a flood of their colleagues said his actions could warrant impeachment.

Trump has acknowledged that he mentioned the Bidens in a call on July 25 with the new Ukrainian leader, Volodymyr Zelenskiy, and people familiar with the call have said Trump repeatedly urged Zelenskiy to speak with one of his personal lawyers, Rudy Giuliani. Giuliani has been pushing Ukraine aggressively to look into the Bidens and the origins of material that implicated Paul Manafort, Trump’s former campaign chairman, in 2016.

Trump, buffeted by questions earlier in the day at the United Nations about his conduct, denied accusations that he had withheld the aid from Ukraine in an attempt to press Zelenskiy to do his bidding. The president also continued to insist he had acted appropriately.

“No, I didn’t — I didn’t do it,” Trump told reporters, when asked whether he had conditioned the aid on the promise of an investigation of unsubstantiated corruption charges against the former vice president and his son. But not long before, the president had suggested that there would be nothing wrong with his linking funding for Ukraine, a former Soviet republic that is fighting Russian-backed separatists, to a corruption inquiry about Biden and his family.

“Why would you give money to a country that you think is corrupt?” Trump said.

It was one of a series of whipsawing declarations Trump made throughout the day Monday as he defended himself, vilified the Bidens and appeared by turns eager and reluctant to reveal the facts at the root of the allegations. Trump first said he hoped that the transcript of a July 25 phone call he had with Zelenskiy would be released, claiming that it would exonerate him, only to angrily deny moments later that he had committed to doing so.

“I hope you get to see it soon,” Trump said, before arguing that making the transcript public would set a bad precedent.

Biden chimed in via the president’s favorite platform, Twitter, responding to Trump’s dismissal of charges of misconduct by writing, “So release the transcript of the call then.”

House Democrats were doing everything they could to try to force Trump’s hand, even as they weighed voting on a resolution this week condemning his actions. At the same time, the chorus of lawmakers demanding impeachment grew louder, underscoring how the latest revelations about the president have touched off a seismic shift under Democrats’ feet.

Seven freshman House Democrats with military and national security experience — most of whom have been reluctant to call for impeachment — spoke out Monday night in a strongly worded opinion article in the Washington Post, saying the House should begin impeachment hearings if necessary to get the information lawmakers need to evaluate the allegations.

“If these allegations are true, we believe these actions represent an impeachable offense,” the lawmakers wrote.

The authors were Reps. Gil Cisneros of California, Jason Crow of Colorado, Chrissy Houlahan of Pennsylvania, Elaine Luria of Virginia, Mikie Sherrill of New Jersey, Elissa Slotkin of Michigan and Abigail Spanberger of Virginia. Crow had previously called for an impeachment investigation, but others, including Slotkin, have been reluctant.

The chairmen of three House committees investigating the matter threatened to issue subpoenas in the coming days if the administration did not hand over a transcript of the call and documents related to the decision to withhold the aid money. A failure to do so — or to disclose to Congress a secretive whistleblower complaint said to be related to the Ukraine matter — would be considered obstruction, they said, an indication that they could consider it grounds for impeachment.

“If press reports are accurate, such corrupt use of presidential power for the president’s personal political interest — and not for the national interest — is a betrayal of the president’s oath of office and cannot go unchecked,” the chairmen of the House Intelligence, Foreign Affairs, and Oversight and Reform committees wrote Monday in a letter to Secretary of State Mike Pompeo.

They added, “By withholding these documents and refusing to engage with the committees, the Trump administration is obstructing Congress’ oversight duty under the Constitution to protect our nation’s democratic process.”

It appeared increasingly likely that the brewing conflict would come to a head Thursday, when the House Intelligence Committee was already scheduled to question Joseph Maguire, acting director of national intelligence, who has withheld the whistleblower complaint under advisement from the Justice Department and the White House. The panel has demanded that Maguire bring with him a copy of it. Now, lawmakers also want a decision by Pompeo — and by extension, Trump — by that day on whether he will furnish a transcript of the presidential conversation, as well as other materials they have requested.

Mindful that Democrats may have only a brief window to decide their course, Speaker Nancy Pelosi summoned the leaders of six House committees involved in investigations of the president to meet Tuesday, telling the lawmakers to come without aides. Afterward, she planned to convene a special meeting of the Democratic caucus to discuss impeachment.

Their decisions could have grave implications for Trump’s presidency.

A growing number of House Democrats said Monday that the new revelations all but demanded the move. They warned that a decision by the Trump administration not to hand over documents about a matter of urgent national security would leave the House with no choice but to initiate full-bore impeachment proceedings. At the same time, they said, any material that corroborated news reports about Trump’s actions could lead to the same outcome.

“It is clear that the sitting president of the United States placed his own personal interests above the national security interests of the United States,” said Rep. Angie Craig of Minnesota, who flipped a Republican seat last fall. She called for impeachment proceedings to begin “immediately, fairly and impartially.”

Craig’s announcement came alongside that of another Minnesota freshman, Dean Phillips, who warned, “If the reports are corroborated, we must pursue articles of impeachment and report them to the full House of Representatives for immediate consideration.”

Slotkin, a former CIA officer who participated in briefings with Presidents George W. Bush and Barack Obama, and who advocated whistleblower protections while working for Bush’s director of national intelligence, said the issue was “personal” for her.

“As national security professionals, this was too much,” she said. “While we had always been judicious in thinking about impeachment before, this just crossed a line.”

Other, more veteran lawmakers, issued similar statements.

Veteran Democrats close to Pelosi, who has stubbornly resisted impeachment, joined the chorus as well. “An impeachment inquiry may be the only recourse Congress has if the president is enlisting foreign assistance in the 2020 election,” said Rep. Rosa DeLauro of Connecticut. “Congress must meet this pivotal moment in our nation’s history with decisive action.”

There were also indications of more movement to come. Other moderate freshmen who have shied away from impeachment spent the day furiously calling one another in efforts to calibrate their responses. Several said privately that they were on the brink of supporting an impeachment process but that they wanted to first see what transpired Thursday.

Privately, some Democrats and their aides were more cautious, fretting that the transcript of the July call would not be as damning as billed. They worried that the anticipation of its disclosure was replicating the dynamic that surrounded the release of the report by Robert Mueller, the former special counsel who investigated Russia’s interference in the 2016 elections, in which Democrats had expected a set of clear-cut revelations that would all but demand Trump’s impeachment but ended up instead with a document that did not move public opinion against the president. They cautioned quietly that Democrats needed to see the evidence before getting too far down the impeachment path.

Democrats got some backup in the Senate from Republicans, who have generally split over whether Trump is obliged to share either the transcript or the whistleblower complaint with Congress.

“I believe the most helpful report would be a transcript of the president’s conversation with President Zelenskiy,” Sen. Mitt Romney of Utah, the 2012 Republican nominee for president, told reporters. “That, I think, would be the most instructive. But I certainly believe that the whistleblower report should also be available to Congress.”

Speaking on the Senate floor Monday afternoon, Sen. Mitch McConnell, R-Ky., the Senate majority leader, accused Democrats of trying to exploit a serious issue for political gain. He said he had confidence that the Senate’s intelligence panel, working quietly on a bipartisan basis, would handle it appropriately.

He called it “regrettable” that Rep. Adam B. Schiff, the House Intelligence Committee chairman, and Sen. Chuck Schumer, the Democratic leader, “have chosen to politicize this issue, circumventing the established procedures and protocols that exist so the committees can pursue sensitive matters in the appropriate, deliberate, bipartisan manner.”

Questions about Ukraine came to dominate a day at the United Nations that was otherwise packed with meetings with foreign leaders and the president’s foreign policy abroad.

During a meeting with President Andrzej Duda of Poland, Trump suggested that his main complaint about the U.S. aid to Ukraine — which he temporarily suspended this summer before releasing it last month amid bipartisan pressure from Congress — involved a lack of European assistance to the country. “Why isn’t Europe helping Ukraine more?” Trump said. “Why is it always the United States?”

The U.S. aid package included about $250 million from the Department of Defense and $141 million from the State Department.

In multiple comments to reporters, Trump sought to deflect attention from his actions and tarnish Biden, a leading contender for the 2020 Democratic presidential nomination.

“What Biden did is a disgrace. What his son did is a disgrace,” Trump said. He later added, “If a Republican ever did what Joe Biden did, if a Republican ever said what Joe Biden said, they’d be getting the electric chair right now.”

The meetings were the first of more than a dozen sit-downs Trump had scheduled with world leaders — including with Zelenskiy of Ukraine, whom he will see Wednesday.

Between events at the U.N. complex, Trump also tweeted an attack against his accusers as “stone cold Crooked.” And he implied that the unnamed intelligence community whistleblower might be a traitor: “Is he on our Country’s side,” Trump wrote. “Where does he come from.”

Without offering proof, Trump also insisted that Hunter Biden, an international business consultant during his father’s time in office, “took money” from China and suggested that the former vice president would strike a softer line toward Beijing as a result. China, Trump said, “can think of nothing they’d rather see than Biden get in.”

There is no evidence that the younger Biden’s business dealings have had any effect on his father’s public policy positions. Trump has seized on the elder Biden’s insistence in 2016 that Ukraine fire its top prosecutor at a time when a Ukrainian company on whose board Hunter Biden sat was suspected of criminal activity. But that prosecutor was widely seen as corrupt and was not aggressively pursuing a case against the company, Burisma Holdings.