Tapes Show Links in Two N.Y. Bomb Plots : Courts: Jury hears exchange between FBI informant, alleged leader in scheme to blow up several landmarks. Reference is made to trade center blast.

For the first time, jurors at the trial of an Egyptian sheik and 10 of his followers heard taped conversations Tuesday between an FBI informant and a leader in an alleged conspiracy charged with plotting “a war of urban terrorism” against the United States.

The recorded conversations--the first of dozens that will be introduced--showed links between the group on trial and four men convicted last year of bombing the World Trade Center in February, 1993, an act that killed six people and injured more than 1,000.

About 150 tapes were made secretly by Emad Ali Salem, an erratic FBI informant whose credibility has been open to challenge since he admitted last week that he sometimes had lied about his accomplishments. It is unclear how many of the tapes prosecutors ultimately will introduce.

The first two tapes were of conversations in May, 1993, between Salem and Siddig Ibrihim Siddig Ali, an alleged top aide to Sheik Omar Abdel Rahman, the principal defendant and spiritual leader of those on trial. However, the longest conversation, read to the jury in English, did not implicate the sheik personally in the alleged terrorism plot, which reportedly included plans to bomb the Lincoln and Holland commuter tunnels and FBI headquarters in Manhattan.

But Siddig Ali, who last month decided to plead guilty and cooperate with the government, tells Salem on the tape that the alleged co-conspirators knew of the trade center plot. He characterizes Mohammed A. Salameh, one of those convicted, as “the stupidest of God’s creatures” for renting a van in his own name to carry a 2,000-pound homemade bomb into the center’s underground garage.

Expressing surprise at the way the bombing was carried out, Siddig Ali says: “The operation was not done by a single person. I mean it was a group effort. We all had confidence in them.”

He does not elaborate on who he means by “we,” but prosecutors are expected to develop that when he testifies later in the trial.

Defense attorneys challenged Salem’s handling of the recordings. They elicited denials from Salem, once the sheik’s confidant, that he had erased or altered any segments. But he admitted he may have started and stopped the tape at odd times and may have mislabeled some tapes by date and place.

Salem said that FBI agents installed a recorder inside a briefcase and equipped his 1989 Pontiac with a second taping system.

Although last year’s trial shed no light on whether foreign sources may have financed the trade center bombing, Siddig Ali tells Salem on the tape that support has come from Sudan and Saudi Arabia. Sudan has been placed on the State Department’s list of countries that export terrorism. As for Saudi Arabia, an ally of the United States, Siddig Ali says that support came from individuals, not from the Saudi government.

“Basically, there is a certain committee. Saudi Arabia, not the government, it is brothers,” he says on the tape, meaning Islamic radicals in that country.

But contrary to implicating the sheik in any terrorist plot, Siddig Ali pictured the blind and diabetic cleric as a devout man of prayer.

Later this week prosecutors are expected to present an FBI videotape showing several defendants mixing chemical explosives in a Queens, N.Y., garage.