Associated Press WriterWASHINGTON (AP) -- On a translated tape released by the Pentagon Thursday, alleged terrorist mastermind Osama bin Laden says "we calculated in advance" the number of casualties in the Sept. 11 attacks.
He also said "we did not reveal" the attack plan to the hijackers until "just before they boarded the planes."
"The brothers who conducted the operation, all they knew was that they have a martyrdom operation and we asked each of them to go to America, but they didn't know anything about the operation, not even one letter," bin Laden said, according to the U.S. translation.
"But they were trained and we did not reveal the operation to them until they are there and just before the boarded the plane," he added.
Bin Laden also said he told his followers there would be more destruction after the first plane hit the World Trade Center.
"They were overjoyed when the first plane hit the building, so I said to them: be patient," he said.
Two bin Laden associates -- spiritual adviser Ayman al-Zawahri and spokesman Abu Ghaith -- also appear in the tape. Their conversation was recorded in what the Pentagon identified as a guest house in Kandahar, Afghanistan.
Prior to releasing the tape, the Pentagon brought in four nongovernment Arabic-speaking translators to listen to bin Laden's remarks and agree on a uniform translation.
The tape lasts about one hour.
Bin Laden said he and his associates had estimated in advance how many people would be killed in the attacks on the World Trade Center towers.
"We calculated that the floors that would be hit would be three or four floors," he said. "I was the most optimistic of them all."
After a section of the tape which the Pentagon called inaudible, bin Laden says, "Due to my experience in this field, I was thinking that the fire from the gas in the plane would melt the iron structure of the building and collapse the area where the plane hit and all the floors above it only. This was all that we had hoped for."
The man U.S. officials say organized the execution of the hijackings on Sept. 11, Mohamed Atta, "was in charge of the group," bin Laden said.
Bin Laden, a Saudi fugitive, also said "we had notification since the previous Thursday that the event would take place that day," referring to the attacks. He then described hearing the news reports.
"We had finished our work that day and had the radio on," he said. "It was 5:30 p.m. our time. I was sitting with Dr. Ahmad Abu-al-Khair. Immediately, we heard the news that a plane had hit the World Trade Center. We turned the radio station to the news from Washington. The news continued and no mention of the attack until the end. At the end of the newscast they reported that a plane just hit the World Trade Center."
He then mentioned hearing the newscast report that a second plane had hit World Trade Center.
"The brothers who heard the news were overjoyed by it."
U.S. intelligence officers found the bin Laden tape in a residence in Jalalabad in eastern Afghanistan. It bears a date stamp that says it was made Nov. 9. That was the day the northern Afghan city of Mazar-e-Sharif fell to the rebel northern alliance.
Several members of the House and Senate Intelligence committees had urged the Bush administration to release the tape, although Rep. Jane Harman, D-Calif., said she was "concerned that the bin Laden tape is damaging to American security."
Harman has said the tape may have been planted and could contain covert messages from bin Laden to his followers, and broadcasting it may play into his hands.
"I would have preferred that its distribution be limited to those with a need to know," Harman said.
Officials had voiced similar concerns about other tapes bin Laden produced, but those were clearly meant for public release. Officials had asked U.S. broadcasters not to air those tapes in their entirety.