Washington ? Lawmakers have postponed what was expected to be the climax of four weeks of public hearings on the Sept. 11 attacks: an open session with the directors of the CIA, FBI and National Security Agency scheduled for today.

The House and Senate intelligence committees said they needed to discuss “more business” from a closed session Wednesday. They didn’t elaborate, but Wednesday’s meeting was believed to include discussions about the FBI’s handling of an informant who was the landlord of two of the Sept. 11 hijackers.

An FBI official, speaking on condition of anonymity, said congressional staff have spoken several times to the agent who handled the informant. But the bureau won’t allow staff to speak to the informant, who has been promised anonymity.

FBI Director Robert Mueller and CIA Director George J. Tenet were to appear at the closed-door session today. The public session will be rescheduled for next week, and the two directors were expected to appear, along with the NSA’s director, Lt. Gen. Michael Hayden.

Tensions between lawmakers and the agencies have built up since the committees’ joint inquiry into the Sept. 11 attacks began in February.

Most recently, members of the Senate panel have said intelligence agencies have not fully responded to requests for information about the threat posed by Iraq. The committee has also pushed for the declassification of some intelligence on Iraq. Some was declassified in a letter released Tuesday night, but the CIA declined to declassify additional material Wednesday.

Since the start of public hearings last month, inquiry staff have criticized agencies for failing to link clues that might have pointed to the attacks. They included a rise in reports of possible terrorist attacks, a July 2001 memo by a Phoenix-based FBI agent warning that al-Qaida terrorists may be undergoing flight training at U.S. schools and the August 2001 arrest of a suspicious student pilot, Zacarias Moussaoui, on immigration charges. Moussaoui has since been charged with conspiring in the attacks.

Also, staff and lawmakers accused the CIA of not doing enough to warn other federal agencies about two of the future hijackers after they were spotted attending an al-Qaida meeting in Malaysia in January 2000.

Former CIA and FBI officials have defended their agencies’ efforts, saying they scored major gains against terrorism despite legal restrictions that hampered their work and inadequate funding for personnel and equipment.