Transcripts of the tapes were turned over last week to defense lawyers in two cases, the ongoing World Trade Center bombing trial and the second case, which involves 15 men accused of plotting to blow up other targets in New York. The transcripts, which were put under seal by a Federal judge, have been obtained by The New York Times.

The transcripts are replete with new allegations about what the authorities have called the most damaging terrorist attack in American history and the larger conspiracy related to it. The transcripts are like spotlights, providing bursts of illumination in the still-dark arena of the case, so that faces, names and actions appear in the light, and then, the moment of illumination over, seem to fade again. Mr. Salem's specific allegations cannot be confirmed independently but they are clearly taken seriously by the F.B.I. agents.

The transcripts show the torment of the F.B.I. agents and of Mr. Salem over whether the attack on the World Trade Center could have been prevented, as Mr. Salem repeatedly and furiously insists, and whether the decision to pull him off the case six months before the explosion was a fatal blunder. Mr. Salem tells the F.B.I. that he himself was recruited into the bombing conspiracy in 1992 by El Sayyid A. Nosair, the man accused of killing Rabbi Meir Kahane in 1990. In Mr. Salem's account, Mr. Nosair emerges for the first time as a central figure in the trade center plot. Mr. Salem also says he knows that Mr. Nosair, who was acquitted of the Kahane killing but sentenced to 7 1/2 to 22 1/2 years in prison on related charges, actually killed Rabbi Kahane.

"He told me," Mr. Salem says.

Mr. Salem also tells the F.B.I. agents that Mr. Nosair first asked Mr. Salem to carry out major roles in the making of a bomb. He suggests that it was when he demurred, arguing that he was too busy with other things, that Mr. Nosair recruited some of the figures now on trial in the World Trade Center case, specifically, Mohammed A. Salameh and Mahmud Abouhalima.

The transcripts also disclose some tantalizing new allegations concerning Sheik Omar Abdel Rahman, who preached in mosques in both Brooklyn and Jersey City that were attended by many of the defendants in the conspiracy case. Mr. Salem says that Mr. Abdel Rahman asked him to assassinate the Egyptian President, Hosni Mubarak. Mr. Salem also alleges that Mr. Abdel Rahman had close contacts with Hamas, the extremist Palestinian organization.