A secret intelligence document prepared for President Bill Clinton in December 1998 reported on a suspected plot by Osama bin Laden to hijack a U.S. airliner in an effort to force the United States to release imprisoned conspirators in the 1993 World Trade Center attacks.

The one-page declassified version of the President's Daily Brief dated Dec. 4, 1998, contains chilling information -- gleaned by the CIA from several sources -- indicating that al Qaeda was working with U.S.-based operatives of its deadly ally, the Egyptian group Gama at al-Islamiyya, in the purported hijacking plot.

The PDB shows that the intelligence community and the White House had been aware of al Qaeda's interest in hijacking U.S. airliners long before the attacks on Sept. 11, 2001. On the day the PDB was prepared, then-CIA Director George J. Tenet said in a memo to the intelligence community that "we are at war" and that no resources should be spared to defeat the terrorists.

When it is released this week, a report by the presidential commission investigating the Sept. 11, 2001, attacks will include the newly declassified document and a previously declassified PDB dated Aug. 6, 2001. It will also contain details of what Philip D. Zelikow, the commission's executive director, described yesterday as an "energetic response" to the hijack threat information by the Clinton administration, including its efforts to determine whether the plot reports were true.

The 1998 document is "the most important PDB about hijacking published before 9/11," Zelikow said. The Aug. 6, 2001, PDB prepared for President Bush mentioned 1998 intelligence concerning a plot by bin Laden "to hijack a U.S. aircraft to gain the release of 'Blind Sheik' Omar Abdel Rahman and other U.S.-held extremists."

The 2001 PDB said intelligence officials "have not been able to corroborate" the plot reports from 1998.

The 1998 PDB is titled: "Bin Laden preparing to hijack U.S. aircraft and other attacks." It was declassified, with redactions, by the White House last Monday at the Sept. 11 panel's request. The text of the 1998 PDB was read to a reporter by an administration official who had access to the declassified document.

It said intelligence reports "suggest Bin Laden and his allies are preparing for attacks in the U.S., including an aircraft hijacking to obtain the release of Shaykh Umar Abd al-Rahman, Ramzi Yousef and Muhammad Sadiq Awda. One source quoted a senior member of Gama at al-Islamiyya (I.G.) saying that as of late October the group had completed planning for an operation in the United States on behalf of bin Laden but that the operation was on hold. A senior bin Laden operative from Saudi Arabia was to visit I.G. counterparts in the United States soon thereafter to discuss options -- perhaps including an aircraft hijacking."

A source who may have been different, the PDB said, referred to a September 1998 plan by I.G. leader Mohamed al-Islambuli to hijack an airliner to free Rahman, then imprisoned in Colorado. Islambuli, who was convicted in 1992 in absentia in Egypt of trying to overthrow the Egyptian government, was suspected in 1998 in an attack the previous year that killed 62 tourists in Egypt. The PDB said that source said in late November 1998 that bin Laden might "implement plans to hijack U.S. aircraft before the beginning of Ramadan on 20 December and that members of the operational team had evaded security checks during a recent trial run at an unidentified New York airport."

Though the CIA and other government agencies were clearly aware of the hijack threat, and though the Federal Aviation Administration distributed a circular referring to it in the summer of 2001, a White House official said yesterday that the Bush national security team was not apprised by the outgoing Clinton administration about the intelligence report on a suspected hijack plot to free Rahman.

"There is no record or recollection of the new White House team having been briefed on that threat information," said an administration official, who said the 2001 memo, based on information provided by the CIA, "is the first record of the new White House having that information."

Richard A. Clarke, who was the White House counterterrorism chief under Clinton and for a few months under Bush, testified before the commission that the Bush national security team was not sufficiently concerned about the threat information before the Sept. 11 attacks. He has cited the 2001 PDB as proof that the Bush team had reason to be concerned about hijack threats. But in her testimony Condoleezza Rice, Bush's national security adviser, played down the importance of the hijack reference in that memo, saying it was based on "old reporting."

The details of that reporting and what the government did about the intelligence will be explored publicly for the first time in the commission's report.

The 1998 PDB said that some members of bin Laden's network had received hijack training but that no group directly tied to bin Laden had carried out a hijacking. "Bin Laden could be weighing other types of operations against U.S. aircraft," the PDB said. In October 1998, the memo said, "the I.G. obtained SA-7 missiles and intended to move them from Yemen into Saudi Arabia to shoot down an Egyptian plane or if unsuccessful a U.S. military or civilian aircraft."

Zelikow said the whole story of the 1998 hijack threat and the government's response will be detailed in the commission's report this week. Previous accounts from that period, including accounts detailed by Clarke and others in the Clinton White House, described a renewed push in early 1999 to get the Taliban to turn over bin Laden to the United States or to a third country, as well as other efforts to capture bin Laden in the spring of 1999.

Researchers Madonna Lebling and Meg Smith contributed to this report.