A new report revealing more of acting White House chief of staff Mick Mulvaney's role in withholding aid to Ukraine — and efforts by top Trump administration officials to get that money released — is a "game changer" that shows the need for witness testimony in the president's impeachment trial, Senate Minority Leader Chuck Schumer said Monday.

"This new story shows all four witnesses that we Senate Democrats have requested" were "intimately involved and had direct knowledge of President Trump's decision to cut off aid and benefit himself," Schumer, a Democrat, told reporters in a press conference at his New York office.

"Simply put, in our fight to have key documents and witnesses in the Senate impeachment trial, these new revelations are a game changer."

The New York Times reported Sunday that Mulvaney was flying with President Donald Trump on Air Force One in June when he emailed his senior adviser to ask, “Did we ever find out about the money for Ukraine and whether we can hold it back?”

The adviser, Robert Blair, emailed back that it could be done, but he warned that they should "[e]xpect Congress to become unhinged," the report said, citing a previously undisclosed email. Assisting Mulvaney execute the hold were Blair and three officials in the White House Office of Management and Budget, Russell Vought, the office's acting head, Michael Duffey, who oversees funding, and lawyer Mark Paoletta, the report said.

The Times' report also showed there was high-level pushback from top Trump officials, including Secretary of State Mike Pompeo, Secretary of Defense Mark Esper and now-former national security adviser John Bolton.

The trio met with Trump in the Oval Office in late August and pressed him to release the aid, with Bolton telling the president, "This is in America's interest," the Times reported, citing an official briefed on the gathering.

Trump responded that he didn't believe Ukraine's new president, Volodymyr Zelenskiy, was a genuine reformer. "Ukraine is a corrupt country," Trump reportedly replied, adding that "We are pissing away our money."

Trump reversed course after news of the freeze became public and House Democrats announced they were investigating the hold.

The White House blocked Mulvaney, Pompeo, Esper, Vought, Bolton, Blair and others from testifying or turning over documents to House impeachment investigators.

Schumer is demanding Senate Majority Leader Mitch McConnell, R-Ky., call Mulvaney, Bolton, Blair and Duffey as witnesses at Trump's Senate trial. Emails made public last week showed that Duffey was the official who told the Pentagon that the president wanted the aid frozen — a request that came just hours after Trump's July phone call with the Ukrainian president that has served as the backbone of the impeachment proceedings against him.

The four witnesses "were intimately involved" with what was going on behind the scenes, Schumer said.

"Let me be clear, this is about getting to the truth," the Democratic leader said. "Will the Senate hold a fair trial or will it enable a cover-up? President Trump, if you are so confident you did nothing wrong, why won't you let your men testify?"

The Senate trial will begin after House Speaker Nancy Pelosi, D-Calif., sends the two articles of impeachment over to the Senate, but it's unclear when exactly that will be. Senators are slated to return to Washington on Jan. 3.

Rep. Jamie Raskin, D-Md., a member of the House Judiciary and Oversight committees, told MSNBC's Katy Tur on Monday that the Times article “vindicates the judgment of the House of Representatives.”

"The New York Times story just fills in a lot more details about the essential narrative that is in the impeachment report coming from the House of Representatives," he said. "And we hope that the Senate would indeed fill in further facts that have since surfaced, you know, after our impeachment of the president."

Rep. Adam Schiff, the Intelligence Committee chairman who led the House impeachment inquiry, tweeted a link to the story and wrote, "Despite the President’s obstruction, additional damning evidence of his abuse of power continues to come to light. The question is whether the Senate will demand to see these and other emails and hear from those who were involved."