Jose Padilla, the former Chicago gang member accused of planning to set off a radiological bomb in the United States, also plotted with some of al Qaeda's highest-ranking operatives to blow up U.S. apartment buildings using natural gas and had sworn to carry out attacks when he was arrested two years ago, according to an unusual release of classified interrogation information by the government yesterday.

The seven-page summary of the case against Padilla, a U.S. citizen, also alleges that he met repeatedly with senior leaders of the al Qaeda terrorist network, including lieutenant Khalid Shaikh Mohammed, the mastermind of the Sept. 11, 2001, attacks, who took a keen interest in Padilla because he speaks English and held a valid U.S. passport.

The allegations were unveiled as part of a vigorous defense of the government's treatment of Padilla, one of two U.S. citizens held for long stretches without charges in the United States as "enemy combatants," without access to courts or lawyers. Their cases are pending before the Supreme Court.

At a Washington news conference, Deputy Attorney General James B. Comey Jr. said information gleaned from interrogations of Padilla and others since his arrest show that he was intent on killing innocents in the United States but "would likely have ended up a free man" if prosecuted in the criminal justice system, because his attorney would have advised him to tell authorities nothing. That would have left authorities without the information they have obtained and with the responsibility of watching Padilla for the rest of his life, Comey said.

The release of information yesterday was not related to the Supreme Court case, Comey said, but was in response to a request for information from Sen. Orrin G. Hatch (R-Utah), chairman of the Senate Judiciary Committee. Nor did yesterday's news conference come in response to criticism last week that new warnings of a heightened terrorist threat were vague and unsubstantiated by new information, he said. The move was approved Friday in a letter to Comey from Deputy Defense Secretary Paul D. Wolfowitz.

"We have decided to release this information to help people understand why we are doing what we are doing in the war on terror and to help people understand the nature of the threat we face," Comey said.

But some legal experts said the effort appeared to be aimed at influencing the Supreme Court, and Padilla's court-appointed attorney attacked the disclosure as "the opening statement in a trial they have refused to allow."

"We can't give our response," said Donna R. Newman, who in February was granted restricted access to Padilla at the discretion of the Pentagon. "They control everything. . . . They zip our lips, they unzip [Padilla's] lips for their own purposes, and they do whatever they want, whenever they want. This is not what the U.S. Constitution had in mind."

Douglas W. Kmiec, a Justice Department official in the Reagan and George H.W. Bush administrations who now teaches constitutional law at Pepperdine University in California, said it is unlikely that the material released yesterday will affect the Supreme Court's decision. The justices heard oral arguments in April in the cases of Padilla and Yaser Esam Hamdi, a U.S. citizen captured on the battlefield in Afghanistan who is also held as an enemy combatant in a military brig in South Carolina.

Under normal protocols, the court already would be drafting opinions, Kmiec said. Instead, the information appears aimed primarily "at the court of public opinion."

"It is important to the attorney general and the Department of Justice that not only the Supreme Court sanction the detention of Jose Padilla as an enemy combatant, but that the public also condone it as necessary," Kmiec said. He added that continuing revelations of prison abuses in Iraq may also have played a role in the information's release.

According to the summary released by the Justice Department, Padilla has admitted during interrogations to meeting Mohammed, who dispatched him and an unidentified accomplice on a mission to blow up as many as 20 apartment buildings by sealing off units, filling them with natural gas and using timers to set off the explosions. New York was the most likely target, but Washington, Florida, Chicago and other targets were discussed, the government alleged. Padilla's accomplice is also in custody, Comey said.

The government alleges that Padilla first came in contact with terrorist operatives during a trip to Saudi Arabia in March 2000, where he met a Yemeni recruiter, and would later meet with much of al Qaeda's top echelon, including Mohammed; military commander Muhammad Atef, who became a mentor on terrorist tactics for Padilla; lieutenant Abu Zubaida; and Ramzi Binalshibh, who coordinated the Sept. 11 attacks.

All are in U.S. custody except Atef, who was killed in a U.S. military strike in Afghanistan and whose body Padilla helped dig out of the rubble.

In March 2000, Padilla told U.S. officials, he made a pilgrimage to Saudi Arabia, where he met an unidentified terrorist recruiter. Padilla made his way to Kandahar, Afghanistan, where his terrorist training allegedly began. The FBI obtained a copy of Padilla's training camp application, completed under an alias and found in a binder with more than 100 others, according to the summary.

At the al Farouq camp that fall, he was trained in firearms, communications, surveillance, explosives and other skills. During this time he met Atef, then al Qaeda's military commander. The two would meet several times, including a session in July or August 2001 when Atef asked Padilla to blow up apartment buildings in the United States, the government alleged.

His partner in that first mission was another al Qaeda operative, Adnan G. el Shukrijumah, a trained pilot and one of seven al Qaeda associates named in the warning issued last week by Attorney General John D. Ashcroft. According to the summary released yesterday, Padilla and Shukrijumah -- who had known each other in the Miami area -- could not get along, and their mission was scrapped.

Shortly after Atef's death in November 2001, Padilla and an unnamed accomplice approached Zubaida with a plan to "travel to the United States and detonate a nuclear bomb they learned to make on the internet," according to the government documents. Zubaida arranged for Padilla and his accomplice to propose the idea to Mohammed.

But both Zubaida and Mohammed believed plans to use nuclear or radioactive material were impractical, and the two al Qaeda leaders steered the volunteers toward blowing up apartment buildings instead. Mohammed envisioned as many as 20 simultaneous explosions, probably in New York, but left the details up to Padilla, the summary says.

According to one version of the plan, involving three high-rise apartment buildings, "they would rent two apartments in each building, seal all the openings, turn on the gas and set timers to detonate the buildings simultaneously at a later time," the summary said.

Padilla insists that "he returned to the U.S. with no intention of carrying out the apartment building operation," according to the government document. "However . . . Padilla does admit that he accepted a terrorist mission from al Qaeda, trained for that operation, and then traveled to the U.S."

Comey said that FBI and Defense Intelligence Agency personnel conducted the interrogations and Padilla was not mistreated.

Staff writers Charles Lane and Susan Schmidt and research editor Margot Williams contributed to this report.

Jose Padilla, a U.S. citizen, was arrested in Chicago in 2002.