But they also urged as short a delay as possible, suggesting that the court continue with jury selection as scheduled on Sept. 29.
Summonses already have been mailed to more than 1,000 potential jurors, prosecutors noted, and the jury selection process is expected to be lengthy.
Once a panel is picked, prosecutors said, the jurors could be dismissed until the start of the trial. They suggested that could come on Jan. 5, the date of Gregory Lee's scheduled return from Iraq.
District Court Judge Robert B. Kugler has scheduled a hearing for Thursday to decide the matter.
The defense witness, Lee, is a former Drug Enforcement Administration agent with experience in terrorism investigations.
He spent several years working in Pakistan, and he aided in the arrest of Ramzi Yousef, the convicted 1993 World Trade Center bomber. Lee testified at Yousef's trial.
Lee, now retired from the DEA, also is an expert in the handling and behavior of informants, the defense said.
He had planned to aid in the cross-examination of two FBI informants who recorded hundreds of hours of conversations with the defendants.
The informants' testimony could be pivotal and, as prosecutors noted yesterday, "it is apparent that the defense intends to try to use Mr. Lee to attack [their] credibility."
The five defendants - all foreign-born Muslims raised in the Philadelphia area - were accused of planning to use a pizza delivery pass to gain access to Fort Dix, then open fire on soldiers.
The five men - Mohamad Shnewer, Serdar Tatar and brothers Shain, Eljvir and Dritan Duka - have pleaded not guilty.
In the recordings, the men discuss attacking Fort Dix and other possible targets, and they talk about how to get firearms, prosecutors said.
The men were arrested in a series of raids in May 2007, after two of the Duka brothers allegedly met one of the informants to buy weapons.
The informants also recorded trips the men took to a Poconos firing range - sessions prosecutors have called "training" for their mission.
The defense has countered that their clients are guilty of nothing more than bluster, and the Poconos trips were innocent, disorganized adventures.
Which story the jurors believe could hinge on the informants, one of whom has been identified as an Egyptian illegal immigrant convicted in a federal bank-fraud case in 2001.
Lee, a reserve in the Army Criminal Investigation Command, is being deployed to Iraq to search for soldiers missing in action.
Kugler previously inquired whether Lee could testify via satellite from Iraq.
Prosecutors said yesterday that the Army would prohibit him from testifying while on active duty in a case that goes "against the interests of the United States."
Contact staff writer Troy Graham at 856-779-3893 or tgraham@phillynews.com.