Mr. Menem denied any involvement last November. His former advisers have insisted that he was determined to solve the case, not cover it up, and that Mr. Bernazzani had said the F.B.I. did not view Mr. Meshabi as a credible witness.

With the case seemingly stalled, Argentina’s Supreme Court in May ordered it reopened, saying it was unreasonable to throw out all the original investigative work because of the Galeano corruption scandal. The court ruled that the investigation had been valid until Oct. 31, 1995, when Mr. Galeano decided to offer the money to Mr. Telleldín.

Judge Corral said an appeals court might decide to retry Mr. Telleldín, a used-car salesman who was acquitted after spending 10 years in jail awaiting trial. Mr. Telleldín said in an interview that he was innocent and that it would be “impossible to prove” that he knew the van he sold was going to be used for the bombing.

Mr. Nisman, meanwhile, is pressing on with his investigation of Mr. El Reda. In the weeks before the bombing, Mr. El Reda shuttled between “safe houses” in Buenos Aires and a red brick house in Foz do Iguaçu, a Brazilian town in the Triple Frontier area where Argentina meets Brazil and Paraguay, investigators said.

From millions of phone call records and the help of an unidentified Hezbollah operative, investigators say they were able to piece together evidence of a terrorist cell involving Mr. El Reda that kept in close contact with Beirut leading up to the bombing.

On the morning of July 1, 1994, Mr. Nisman said, Mr. El Reda made a call from the international airport here to a cellphone registered in Foz do Iguaçu, a call that may have set off the final phase of the attack.

Other calls to the cellphone were made from public phone centers near the Jewish community center and near a mosque in Buenos Aires where the cultural attaché at the Iranian Embassy, one of the people charged in 2006, spent a great deal of time, Mr. Nisman wrote in court papers. Mr. El Reda had forged close ties with the Iranian attaché, Mr. Nisman said.