ALEXANDRIA, Va. (AP) — Court-appointed lawyers for terrorism suspect Zacarias Moussaoui have asked a federal judge to dismiss charges against him as punishment for the government's refusal to produce al-Qaida witnesses for the trial.

In a written motion unsealed Wednesday, the lawyers said al-Qaida prisoners would testify that Moussaoui was not involved in planning either the Sept. 11, 2001, attacks or a later operation.

They said government's refusal to allow the captives to testify would deny Moussaoui a fair trial and could unjustly lead to his execution.

U.S. District Judge Leonie Brinkema is on the verge of punishing the government for defying her orders to allow Moussaoui to question three captives. Moussaoui had petitioned to question Khalid Shaikh Mohammed, who is considered the mastermind of the Sept. 11 attacks; his key planner, Ramzi Binalshibh; and Mustafa Ahmed al-Hawsawi, a suspected paymaster for al-Qaida.

Indicted in the only U.S. case arising from the Sept. 11 attacks, Moussaoui has denied charges that he conspired with the hijackers who carried out the plot.

The government has said in court papers that the French citizen was part of a broad terrorist conspiracy, which ranged beyond Sept. 11 and may have included plans for him to fly a plane into the White House.

"However, even assuming that the indictment is sufficiently broad to encompass a post-Sept. 11 attack, dismissal of the indictment nevertheless is required because ... witnesses (names blacked out) exculpate Moussaoui from any later operation as well," the defense motion said.

It added that since a later plan "never took shape and no one died from it," the al-Qaida witnesses could end any justification for the death penalty.

Moussaoui is representing himself, but the court has appointed an experienced defense team to represent his interests in the potential death penalty case.

The defense team, the government and Moussaoui were ordered to submit arguments on the appropriate punishment that could include dismissal of all charges. The district judge's ruling won't be the last word, however, since a federal appeals court panel already has indicated it would intervene after Brinkema imposed her sanctions -- and the losing side could ask the Supreme Court to review the witness access issue.

The filing said the Sept. 11 attacks "form the heart of the government's case."

"Thus, any evidence that moved Moussaoui out of an intended role in, or knowledge of, the specific operation on Sept. 11 greatly diminishes the chance that a jury would, or could, convict him."