Federal prosecutors said Wednesday that they would try for a third time to convict six men accused of conspiring to destroy the Sears Tower in Chicago and join the ranks of Al Qaeda.

Judge Joan A. Lenard said the next trial would proceed in ''the late fall or early winter.''

In the previous trials, government lawyers contended that the men -- Narseal Batiste, Patrick Abraham, Burson Augustine, Rotschild Augustine, Naudimar Herrera and Stanley G. Phanor -- wanted to wage a ''ground war'' against American citizens and had pledged their loyalty for Islamic extremism to F.B.I. informants posing as members of Al Qaeda.

Defense lawyers asserted that their clients had been goaded into making radical remarks and vows of allegiance by the informants. Testimony in the trials revealed that an F.B.I. search of the group's headquarters in the Liberty City neighborhood of Miami yielded no weapons or evidence of preparation for a large-scale attack.

In his appeal for a third trial, the prosecutor Richard Gregorie recalled how Mr. Batiste had been heard in taped conversations saying he ''wanted to kill all the devils,'' a reference to Americans, prosecutors say. ''The United States has decided it is necessary to proceed one more time,'' Mr. Gregorie said.

At the first trial, which ended in December 2007, a seventh defendant, Lyglenson Lemorin, was acquitted, and the jury was unable to come to a unanimous decision about the remaining six. A second trial ended last week with jurors again unable to decide.

On Tuesday, Mr. Herrera was released on $50,000 bond. Rotschild Augustine, an illegal immigrant, was denied bond. The other four had not filed applications for bond.

Prof. Jonathan Turley of George Washington Law School, a critic of the Bush administration's handling of terrorism-related cases, said that by seeking a new trial the government was hoping to justify ''previous headlines'' about evidence -- including wiretaps and informant reports -- presented by Attorney General Alberto R. Gonzales after the suspects' arrest in June 2006.

''These are the types of prosecutors Las Vegas is built on,'' Mr. Turley said. ''They keep returning to the table with the same losing hand.''

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