The House Judiciary Committee voted along party lines to have a subpoena prepped and ready to go for acting Attorney General Matthew Whitaker's hearing Friday, prompting Whitaker to threaten he wouldn't appear unless the panel guaranteed he wouldn't be subpoenaed.

Republicans expressed concern about what precedent a prepackaged subpoena might set for future witnesses, but Chairman Jerrold Nadler, D-N.Y., said at a markup Thursday the subpoena will only be used if Whitaker "refuses to answer legitimate questions," including those on his conversations with President Trump regarding special counsel Robert Mueller’s Russia investigation.

The resolution passed by a 23-13 margin after Democrats killed a GOP-backed amendment to also prepare a subpoena for Deputy Attorney General Rod Rosenstein.

"This resolution is important, although I hope not to have to use it,” Nadler said in his opening statement. “It authorizes the issuance of a subpoena to acting Attorney General Matthew Whitaker to compel both his appearance and his cooperation at tomorrow’s Department of Justice Oversight hearing.”

"The resolution does not cause the subpoena to be issued,” Nadler added. “I hope and expect that this subpoena will not be necessary — but unfortunately, a series of troubling events over the past few months suggest that we should be prepared.”

In response to the subpoena threat, the Justice Department announced Whitaker would only appear if the committee promised not to subpoena him for refusing to answer questions.

“We seek a written assurance from your office that the committee will not issue a subpoena to the acting attorney general on or before Feb. 8, and that the committee will engage in good-faith negotiations with the department before issuing such a subpoena,” the Justice Department wrote in a letter to Nadler.

Nadler provided Whitaker with questions in advance, giving him the chance to consult the White House on whether there were instances where Trump wanted to invoke executive privilege, but Whitaker never responded to Nadler.

Although Republicans were confident Whitaker would appear on Friday, Nadler cited that the Whitaker’s appearance had been postponed from January and claimed the committee received reports that Whitaker was advised by the Justice Department to skip the hearing. Nadler said “such a development should be unacceptable to Democrats and Republicans alike” if Whitaker was absent Friday.

Republicans led by House Judiciary Committee ranking member Doug Collins, R-Ga., voiced opposition to the resolution, claiming it was premature and unnecessary because Whitaker has yet to indicate he would not answer certain questions.

“This subpoena is nothing short of political theater, choreographed by the chairman and starring the acting attorney general as some mythological protector of secrets,” Collins said. “Nothing could be further from the truth. I cannot recall a single instance in which this committee authorized a subpoena for an attorney general for the sole purpose of forcing him to invoke a privilege or risk revealing his conversations with the president.”

Whitaker was named acting attorney general after Trump ousted former Attorney General Jeff Sessions, who had recused himself from the Russia investigation. Rosenstein oversaw the probe before Whitaker became acting head of the Justice Department.

On Thursday, Republicans also attempted to prepare a subpoena for Rosenstein, who was appointed to oversee Mueller's investigation and did so for approximately 15 months before Whitaker took charge of the agency.

“If you’re going to go through with this, add Mr. Rosenstein's name so we can ask him some important questions that the American people need to know,” Rep. Jim Jordan, R-Ohio, argued during the markup of the resolution Thursday.

But Democrats ultimately killed the amendment after Nadler ruled the proposed amendment was not germane to the resolution and an appeal was tabled.

The hearing Friday is expected to be Whitaker's only appearance before Congress as acting attorney general. Trump's attorney general nominee William Barr is expected to be confirmed by the Senate by next week.