WASHINGTON (AP) — A legal showdown over the derailed plea deal for Hunter Biden continued Tuesday as prosecutors asserted that an agreement on a gun charge is dead along with the rest of the deal as the case makes a major shift into a special counsel investigation.

While the agreement that was supposed to have wrapped up the long-running investigation of President Joe Biden's son largely unraveled during a contentious court hearing last month, prosecutors said the two sides had continued to negotiate until the defense rejected their final counterproposal the day before U.S. Attorney David Weiss asked to be named special counsel.

Lawyers for Hunter Biden have argued that prosecutors reneged on an agreement on tax charges but said a separate agreement sparing him prosecution on a gun charge remains valid. The agreement on the gun charge also contains an immunity clause against federal prosecutions for some other potential crimes.

Prosecutors denied reneging on any deal. While the agreement on the gun charge was signed by a prosecutor, probation agents didn't sign it and so it never became valid, they argued.

The conflict is now in front of U.S. District Judge Maryellen Noreika, who is weighing the prosecution's motion to pull the tax misdemeanor charges they filed and potentially file them in another court like California or Washington.

Biden's defense attorney on the case, Christopher Clark, also filed to withdraw from the case Tuesday, saying that he could be called as a witness over the negotiation and drafting of the deal and cannot also act as his lawyer. He's been replaced by another Hunter Biden attorney, Abbe Lowell.

The plea agreement had been decried as a "sweetheart deal" by Republicans who are pursuing their own congressional investigations into nearly every facet of Biden's business dealings and the Justice Department's handling of the case.

The agreement had originally called for Biden to plead guilty to failing to pay taxes on over $1.5 million in income in both 2017 and 2018, and get probation rather than jail on the misdemeanor counts. A separate agreement was to spare him prosecution on the felony crime of being a drug user in possession of a gun in 2018 if he kept out of trouble for two years.

Attorney General Merrick Garland's surprise announcement last week of Weiss as special counsel raised fresh questions about the case ahead of the 2024 election. Hunter Biden's history of drug use and financial dealings have trailed the political career of his father.

The case comes against the backdrop of the Justice Department's indictments against former President Donald Trump — Joe Biden's chief rival in next year's election.

Trump has been indicted and is awaiting trial in two separate cases brought by special prosecutor Jack Smith. One is over Trump's refusal to turn over classified documents stored at his Mar-a-Lago estate. The other involves charges of fraud and conspiracy to overturn the 2020 election in the run-up to the Jan. 6, 2021, attack on the U.S. Capitol.

In the case of Hunter Biden, prosecutors have not made any accusations or charges against the president in probing the affairs of his son. House Republicans have been trying to connect Hunter Biden's work to his father, but have not been able to produce evidence to show wrongdoing.