After a tense back-and-forth between congressional Democrats and the Justice Department, House Judiciary Committee Chairman Jerry Nadler and the DOJ announced Thursday evening that Acting Attorney General Matthew Whitaker, likely in his final days as the country's chief law enforcement officer, will appear Friday as scheduled before the panel.

House Democrats had threatened to subpoena Whitaker's testimony about Special Counsel Robert Mueller's Russia probe, and in response, Whitaker -- who previously had agreed to testify -- warned that he wouldn't show up unless lawmakers dropped the ultimatum he described as "political theater."

In a letter to Whitaker on Thursday, Nadler, D-N.Y., wrote, "If you appear before the Committee tomorrow morning and if you are prepared to respond to questions from our Members, then I assure you that there will be no need for the Committee to issue a subpoena on or before February 8."

He continued: "To the extent that you believe you are unable to fully respond to any specific question, we are prepared to handle your concerns on a case-by-case basis, both during and after tomorrow’s hearing."

Although it appeared possible that those statements might have fallen short of the assurances Whitaker was seeking, Nadler wrote on Twitter late Thursday that Nadler would, indeed, make an appearance at 9:30 a.m. ET.

But in a bizarre twist, Fox News has obtained a separate letter that Nadler sent to Whitaker earlier in the day, which explicitly states that Whitaker can testify without a subpoena and that there is "no need" for a subpoena. While the committee's GOP majority was copied on the letter, Fox News is told Republicans never actually received it.

The DOJ later said in a statement: "The Chairman has made the commitment that we requested, and agreed that, if Mr. Whitaker voluntarily appears at tomorrow’s hearing, the Committee will not issue a subpoena on or before February 8. In light of that commitment, Acting Attorney General Whitaker looks forward to voluntarily appearing at tomorrow’s hearing and discussing the great work of the Department of Justice."

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Nadler had approved a tentative subpoena to ensure that Whitaker appeared Friday and answers questions. But, for several hours on Thursday, it appeared possible Whitaker would not show up, leaving representatives to either cancel the hearing or ask questions to an empty chair.

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The vote by the committee didn't issue a subpoena but allowed Nadler to do so if Whitaker was uncooperative. Nadler said he hoped not to have to use the subpoena, but said, "a series of troubling events over the past few months suggest that we should be prepared."

House Judiciary Committee Chairman Rep. Jerrold Nadler D-N.Y., during the panel's debate over a subpoena Thursday. (AP Photo/Jose Luis Magana)

The New York Democrat said that as late as last week the committee had received reports that some at the department were counseling Whitaker not to appear.

Whitaker insisted Thursday that he had "devoted considerable resources and numerous hours to my preparation" and was looking forward to the hearing. He criticized the committee for prematurely and unnecessarily authorizing a subpoena for him even though he had agreed to appear.

"Weeks ago, in good faith, I voluntarily agreed to appear and testify on February 8 before the House Judiciary Committee," Whitaker wrote to Nadler on Thursday afternoon. "Unfortunately, the Committee now has deviated from historic practice and protocol and taken the unnecessary and premature step of authorizing a subpoena to me, the Acting Attorney General, even though I had agreed to voluntarily appear."

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A Justice Department spokesperson told Fox News earlier this week that Whitaker had, in fact, accepted Nadler’s invitation to testify in public.

And, senior Justice Department officials told Fox News that Whitaker had been engaged in “robust” preparations for his appearance before the committee for weeks, including several mock hearings and briefings from all components within the Justice Department.

Acting Attorney General Matthew Whitaker, center, acting Secretary of Defense Patrick Shanahan, right, and members of President Donald Trump's cabinet at the State of the Union address Tuesday night. (AP Photo/Andrew Harnik)

Whitaker added: "Such unprecedented action breaches our prior agreement and circumvents the constitutionally required accommodation process. Based upon today's action, it is apparent that the Committee's true intention is not to discuss the great work of the Department of Justice, but to create a public spectacle. Political theater is not the purpose of an oversight hearing, and I will not allow that to be the case."

Democrats have said they want to talk to Whitaker because he is a close ally of Trump who has criticized Mueller's Russia investigation, which he oversees.

They are calling him to testify even though his time leading the Justice Department is ending, with the Senate expected this month to confirm Trump's nominee for attorney general, William Barr. The Senate Judiciary Committee voted along party lines Thursday to approve Barr's nomination, sending the pick to the full Senate.

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Republicans strongly opposed Nadler's resolution to approve a subpoena if necessary. They said it was unnecessary because Whitaker was already appearing voluntarily.

Georgia Rep. Doug Collins, the top Republican on the panel, called the subpoena authorization "political theater" before the vote. Collins said it was "choreographed by the chairman and starring the acting attorney general as some mythological protector of secrets."

After Whitaker's statement, Collins said Nadler had overplayed his hand.

"In a quest to score political points against the president, they authorized a pre-emptive subpoena, treating a voluntary witness as hostile," Collins said.

In a separate letter sent to Nadler, Assistant Attorney General Stephen Boyd demanded a response on the subpoena question. Boyd also responded to Nadler's request for notification if Whitaker planned to assert executive privilege on certain topics.

Boyd laid out an argument for asserting such executive privilege in the letter, saying that administration officials from both parties have declined to answer questions about conversations they have had with the president.

"Rather than conducting appropriate oversight into the department's programs and activities, the committee evidently seeks to ask questions about confidential presidential communications that no attorney general could ever be expected to disclose under the circumstances," Boyd wrote.

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Nadler had noted that previous Trump administration officials, including former Attorney General Jeff Sessions, declined to answer questions about conversations with the White House during testimony, saying that the president might want to claim executive privilege on those conversations in the future. Nadler said that was "ridiculous" and administration officials needed to provide the committee with answers or a better excuse to withhold them.

"Without the threat of a subpoena, I believe it may be difficult to hold Mr. Whitaker to this standard," Nadler said.

Fox News' Brooke Singman, Catherine Herridge, Adam Shaw, Jake Gibson and The Associated Press contributed to this report.