Fox News contributor Ken Starr said on Friday that acting Chief of Staff Mick Mulvaney was “pretty close” to admitting President Trump’s phone call with Ukrainian leader Volodymyr Zelenksy did involve a “quid pro quo.”

Starr went on to say, “But now Mick Mulvaney may find himself under oath and instead of just the give-and-take with the press, he’s going to now have to say precisely what happened,” the former independent counsel told “America’s Newsroom.”

Mulvaney seemed to contradict Trump’s claim that there had been no “quid pro quo” during his July 25 phone call with Zelensky, by telling reporters at the White House Thursday that the release of military aid to Ukraine was tied to the administration’s demands that Kiev investigate purported corruption by the Democrats during the 2016 presidential election campaign.

FLEISCHER: MICK MULVANEY MADE A 'TERRIBLE MISTAKE' BY CONTRADICTING THE PRESIDENT

When questioned by reporters about the administration’s decision to withhold $400 million in aid from Ukraine, Mulvaney said that Trump told him at the time: "This is a corrupt place. Everyone knows this is a corrupt place ... Plus, I'm not sure that the other European countries are helping them out either.”

Mulvaney added: “Did [Trump] 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 ... The look back to what happened in 2016 certainly was part of the thing that he was worried about in corruption with that nation. And that is absolutely appropriate.”

MULVANEY COMMENTS SEIZED ON BY CRITICS SAYING IT'S PROOF OF UKRAINE QUID PRO QUO

Mulvaney later walked back the statements, stating clearly that there was no "quid pro quo."

Starr said that there needed to be greater discipline in the messaging in regard to the impeachment inquiry of Trump.

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“Self-discipline; the stakes are extremely high. The impeachment train is on the tracks and it's rolling toward the station. Everyone needs to be watchful and careful and guarded,” he said.

Fox News' Andrew O'Reilly contributed to this report.