WILMINGTON, Del. — Hunter Biden’s plea deal hit a major roadblock during an unexpectedly contentious federal court hearing Wednesday as prosecutors and Biden’s attorneys initially disagreed about the scope of the agreement and the judge then balked at approving the deal.

After pressing both sides for details about the deal, U.S. District Judge Maryellen Noreika adjourned the hearing so that the two sides could refine and clarify the agreement — under which the president’s son had planned to plead guilty to two misdemeanor tax offenses and likely avoid punishment on a felony gun charge.

At the end of the tumultuous three-hour hearing, Biden instead wound up pleading not guilty to the tax charges, and the judge postponed further proceedings, likely for a month or more. The deal isn’t dead, but federal prosecutors and Biden’s lawyers will now have to satisfy Noreika’s concerns about technical aspects of the deal and her own role in enforcing a so-called diversion agreement, under which Biden would avoid prison time on the gun charge if he remains drug-free for two years.

The judge made clear that she viewed the deal between Biden’s lawyers and the Justice Department as outside the norm.

“These agreements are not straightforward, and they contain some atypical provisions,” Noreika said as the hearing reached a close.

Biden faces federal criminal charges for willfully failing to file or pay his income taxes in 2017 and 2018 and for owning a handgun in 2018 — a time when he has admitted he was regularly using cocaine. Federal law prohibits drug users from possessing firearms.