Deputy Assistant Secretary of Defense Laura Cooper testified last month that Pentagon officials began receiving "phone calls from industry" -- apparently referring to private companies that supply weapons and military hardware to the government -- after President Trump initiated a hold on military aid to Ukraine earlier this year.

The revelation, which came in a transcript of Cooper's closed-door Oct. 23 deposition released Monday by House Democrats as part of their impeachment inquiry, prompted concerns from commentators that the most self-destructive elements of the Russia probe were resurfacing.

"Like Russiagate, Ukrainegate enrolls liberals in the Cold War designs of dangerous hawks and neocons," tweeted journalist Aaron Mate.

Additionally, Cooper testified that the Trump administration had pushed Ukraine to issue a public statement disavowing any efforts to influence U.S. elections -- but Cooper stopped short of saying that officials wanted to include a reference to Joe and Hunter Biden's business dealings in the country.

Previous testimony in the inquiry has suggested that the White House improperly pressured Ukraine to implicate the Bidens publicly. Former U.S. envoy to Ukraine Kurt Volker, for example, had remarked that European Union envoy Gordon Sondland and Trump attorney Rudy Giuliani worked with a top Ukrainian aide to include a reference to the Biden-linked Ukrainian natural gas company Burisma Holdings.

But, Cooper said that on Aug. 20, Volker met with her -- and the idea of mentioning the Bidens apparently didn't come up.

"In that meeting, he did mention something to me that, you know, was the first about, somehow, an effort that he was engaged in to see if there was a statement that the government of Ukraine would make that would somehow disavow any interference in U.S. elections and would commit to the prosecution of any individuals involved in election interference," Cooper said. "And, that was about as specific as it got."

Cooper's testimony was made public as House Democrats on Monday also released transcripts from their interviews with Christopher Anderson, a career foreign service officer at the State Department, and Catherine Croft, a Ukraine expert at the State Department. Croft testified that she speculated Trump would be willing to shift Ukraine policy to hurt a Biden candidacy, and that news of a holdup of Ukraine aid "blew up" a State Department meeting.

READ COOPER'S TESTIMONY TRANSCRIPT

Croft, in her remarks, said that the Office of Management and Budget had "reported that the White House chief of staff, Mick Mulvaney, had placed an informal hold on security assistance to Ukraine. The only reason given was that it came at the direction of the president."

Separately, Cooper testified about Defense Department concerns that Trump's temporary withholding of military aid to Ukraine may have been illegal.

"I'm not an expert on the law, but in that meeting immediately deputies began to raise concerns about how this could be done in a legal fashion because there was broad understanding in the meeting that the funding -- the State Department funding related to an earmark for Ukraine and that the DOD funding was specific to Ukraine security assistance," Cooper testified, concerning a July 23 meeting of national security officials. "The comments in the room at the deputies' level reflected a sense that there was not an understanding of how this could legally play out, and at that meeting, the deputies agreed to look into the legalities and to look at what was possible."

The legalities likely regarded the issue of "impoundment" – the requirement that the president either had to spend the money or "impound" it. The White House was coming up against an impoundment deadline when it released the funds for Ukraine.

Moreover, Cooper said, Defense Department officials were concerned that Trump's decision would weaken a "strategic partner."

"I mean, so DOD was concerned about the obligation of funds," she said. "Policy, my team, we were also concerned about any signal that we would send to Ukraine about a wavering in our commitment. ... They are trying to negotiate a peace with Russia, and if they are seen as weak, and if they are seen to lack the backing of the United States for their Armed Forces, it makes it much more difficult for them to negotiate a peace on terms that are good for Ukraine."

She added: "My sense is that all of the senior leaders of the U.S. national security departments and agencies were all unified in their — in their view that this assistance was essential, and they were trying to find ways to engage the president on this."

Croft, meanwhile, told House investigators, "If this were public in Ukraine it would be seen as a reversal of our policy and would, just to say sort of candidly and colloquially, this would be a really big deal, it would be a really big deal in Ukraine, and an expression of declining U.S. support for Ukraine."

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Ukraine had satisfied all necessary benchmarks to obtain Ukraine Security Assistance Initiative funding, Cooper told lawmakers. This past May, Cooper said, Under Secretary of Defense for Policy John Rood "provided the certification to Congress, but that was after coordination with the State Department."

Cooper also told investigators she could make a "very strong inference" that Ukraine was aware in August that the Trump administration was holding up the financial assistance, shortly before the aid was released in September. The Ukraine aid was suspended temporarily in August -- two weeks before the White House released it, Politico reported.

"It could have been my inference, yes, a very strong inference that there was some knowledge on the part of the Ukrainians," Cooper testified. She called the aid suspension, which came without an explanation to her knowledge, "unusual."

Military aid to Ukraine, Cooper further testified, was relevant to U.S. national-security interests.

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"Ukraine, and also Georgia, are the two front-line states facing Russian aggression," Cooper said. "In order to deter further Russian aggression, we need to be able to shore up these countries' abilities to defend themselves. That's, I think, pure and simple, the rationale behind our strategy of supporting these countries. It's in our interest to deter Russian aggression elsewhere around the world."

Trump's suggested in his July call with Ukrainian President Volodymyr Zelensky that the country investigate Joe and Hunter Biden's business dealings there, after it emerged that Joe Biden, the former vice president and current 2020 presidential candidate, had pressured Ukraine to fire its top prosecutor while Hunter Biden held a lucrative role on the board of a Ukrainian natural gas company. Zelensky has said he felt no improper pressure during the call.

In a statement, top House Democrats leading the impeachment inquiry noted that Cooper's testimony indicated that Trump's Ukraine policy angered some officials in the administration.

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“Deputy Assistant Secretary of Defense Laura Cooper testified that President Trump, through the Office of Management and Budget, directed the freeze on hundreds of millions of dollars of critical military aid for Ukraine, against the judgment of career officials in the Department of Defense, Department of State, and other relevant agencies," read the statement, issued by House Intelligence Committee Chairman Adam Schiff of California, Foreign Affairs Committee Chairman Eliot Engel of New York and Oversight Committee Acting Chair Carolyn Maloney of New York.

"Cooper also told the committees that she raised concerns, as did others on several occasions, to senior U.S. government officials about the legality of withholding the congressionally-authorized money, and the challenges that White House delays would put on spending it," the Democrats continued.

Fox News' Mike Emanuel, Jared Halpern, Bill Mears, Sally Persons and The Associated Press contributed to this report.