U.S. Judge Maryellen Noreika deferred the plea deal negotiated by Hunter Biden's attorneys and federal prosecutors after a contentious hearing, taking issue with the structure of the arrangement and lamenting on multiple occasions the deal's "form over substance."

In the interim, Hunter Biden entered a not guilty plea. Noreika requested additional briefings from the parties in the coming weeks before determining next steps.

"I'm not going to say I'm going to accept the agreement, I'm not going to say I'll deny it," she said.

The three-hour hearing featured several turbulent interludes. Noreika's line of questioning about an immunity agreement exposed fissures between the two parties, with the discussion culminating in prosecutors threatening to bring foreign agent charges, prompting Chris Clark, an attorney for Biden, to say: "As far as I'm concerned, the plea agreement is null and void."

After a brief recess, the parties moved past those disagreements. Clark acquiesced to the government's position that any immunity of Hunter Biden would only include tax, firearm, and drug-related conduct investigated by the government.

Judge Noreika asked the parties to consult and brief her in the coming weeks.

In the understatement of the day, Noreika acknowledged that her probing threw "a little bit of a curveball" into the proceeding.

In a dramatic scene in court, the plea deal struck by Hunter Biden fell apart amid the judge's concerns over the terms of the agreement.

Hunter Biden pleaded not guilty to the charges.

U.S. District Judge Maryellen Noreika had raised concerns about the parties linking the tax plea agreement to the deal on the gun charge, and over whether or not a provision in the deal would grant Hunter Biden blanket immunity, meaning that the government would not prosecute him further.

There is no plea deal in the Hunter Biden case.

A deal between federal prosecutors and Hunter Biden is in jeopardy of falling apart.

There is now a brief recess as the parties try to come to terms.

-Olivia Rubin

Less than 24 hours before Hunter Biden was expected in federal court, the judge overseeing his case threatened his legal team with sanctions after she found that a staffer might have "misrepresented her identity" in communications with the court clerk.

The bizarre saga played out Tuesday on the court's public docket, where Ted Kittila, an attorney for the GOP-led House Ways and Means Committee, shared Hunter Biden's taxpayer information as part of an effort to intervene in the case.

Chris Clark, an attorney for Hunter Biden, asked Kittila to seal the information, and when Kittila refused, a member of the firm representing Hunter Biden reached out to the court seeking to have it removed from the docket.

Judge Maryellen Noreika wrote late Tuesday that, having "discussed the matter with the relevant individuals," Jessica Bengels, an attorney with Clark's firm, "represented that she worked with Mr. Kittila and requested the amicus materials be taken down."

"It appears that the caller misrepresented her identity and who she worked for in an attempt to improperly convince the Clerk's Office to remove the amicus materials from the docket," Noreika wrote.

Noreika asked Hunter Biden's legal team to explain why she should not level sanctions against them. In response, Matthew Salerno, an attorney for Biden, called it "an unfortunate and unintentional miscommunication," dispelling Noreika's suggestion that it might have been a nefarious ploy to have a docket entry suppressed.

"We have no idea how the misunderstanding occurred," wrote Salerno. "But our understanding is there was no misrepresentation."

ABC News' Lucien Bruggeman