Senator Chuck Schumer of New York, the Democratic leader, has portrayed Mr. Blair and Mr. Duffey as two of the four key witnesses he believes the Senate should call in Mr. Trump’s impeachment trial, along with Mr. Mulvaney and John R. Bolton, Mr. Trump’s former national security adviser. Senator Mitch McConnell, Republican of Kentucky and the majority leader, has expressed opposition to calling witnesses and again criticized the House investigation on Friday.

The Trump administration’s move to withhold all the emails in full — not even disclosing the dates they were sent, or the shape of paragraphs covered by black lines — is a step beyond its heavy censorship of a related set of emails it released in response to another Freedom of Information Act lawsuit brought by the Center for Public Integrity.

The documents released to the center consisted of about 300 pages of emails between the Office of Management and Budget and the Pentagon about the Ukraine aid package. While the officially released version was heavily redacted — and the center is contesting the censorship in further litigation — the visible portions showed, among other things, that Pentagon officials had worried that holding the funds could be an illegal impoundment.

A report on Thursday by the legal policy website Just Security added further fuel to the controversy by revealing what was under some, but not all, of the deletions. The website said it had been shown some of the emails in unredacted form, including an Aug. 30 message from Mr. Duffey to a Pentagon budget official stating that there was “clear direction from POTUS” — an acronym referring to the president of the United States — “to continue to hold” the Ukraine military assistance.

The Times separately reported this week that Mr. Blair warned Mr. Mulvaney to “expect Congress to become unhinged” if the White House went ahead with the hold on the aid.

Earlier on Friday, Mr. Schumer went to the Senate floor to praise the reporting by The Times, the Center for Public Integrity and Just Security as an additional reason for the Senate, as part of Mr. Trump’s trial, to seek documents and testimony that the White House had blocked House impeachment investigators from obtaining.

“What constituted clear direction?” Mr. Schumer asked. “Did he get an order from the president, or did someone like Mr. Mulvaney get an order from the president passed on to Mr. Duffey? Was there discussion among officials about covering up for the president in delay of military assistance? These are questions that can only be answered by examination of the documentary evidence and by the testimony of key Trump administration officials under oath in a Senate trial.”