Mick Mulvaney, the acting White House chief of staff, acknowledged Thursday that President Donald Trump held up a military-aid package to Ukraine in part because he wanted the Ukrainian government to investigate unfounded conspiracy theories related to the 2016 election.

Mulvaney said three factors drove the decision to withhold aid, including Trump's belief that Ukraine is a "corrupt place" and that other European countries don't contribute enough to its defense.

Mulvaney also said: "Did he also mention to me in the past the corruption related to the DNC server? Absolutely. No question about that. But that's it. And that's why we held up the money."

Mulvaney's statement was the first public acknowledgment from an administration official that Trump held up Ukraine's security assistance in part for political gain.

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Mick Mulvaney, President Donald Trump's acting chief of staff, confirmed that part of the reason Trump withheld military aid to Ukraine was that he wanted the Ukrainian government to investigate a conspiracy theory related to the 2016 election.

Mulvaney acknowledged the quid pro quo during a press conference Thursday in which he explained the factors that contributed to Trump's decision to withhold aid.

Mulvaney said Trump told him that he believed Ukraine was a "corrupt place" and that he didn't want to "send them a bunch of money." He also said the president was concerned that other European countries weren't doing their fair share to contribute to Ukraine's defense.

Mulvaney added: "Did he also mention to me in the past the corruption related to the DNC server? Absolutely. No question about that. But that's it. And that's why we held up the money."

ABC News' Jonathan Karl immediately followed up and asked Mulvaney to confirm that "the demand for an investigation into the Democrats was part of the reason that he ordered to withhold funding to Ukraine."

Mulvaney replied affirmatively, saying that "the look back to what happened in 2016 certainly was part of the thing that he was worried about in corruption with that nation."

Mulvaney's mention of a "DNC server" points to a debunked conspiracy theory about the origins of the FBI's Russia investigation.

The theory claims that the Democratic National Committee hid an incriminating server from the FBI while the bureau was investigating Russia's hack during the summer of 2016, one that contains information about who was really responsible for the breach.

The DNC turned over all its data to the FBI after it learned it had been hacked. That information, moreover, wasn't stored on a single, physical server, but rather on a network of computer systems.