The Justice Department has revealed that two of the men charged in the 1980 assassination here of exiled Iranian diplomat Ali Akbar Tabatabai were overheard during foreign intelligence electronic surveillance conducted by the FBI.

The government has refused to disclose the contents of the conversations, creating a dispute with defense attorneys who say the material could help them prepare their defense.

Lawyers in the case say this is believed to be the first time defense attorneys in a state-level trial court have asked for such surveillance data in a criminal proceeding under the 1978 Foreign Intelligence Surveillance Act.

The defendants -- Ahmed Rauf, also known as Horace A. Butler, and Ali Abdul-Mani, also known as Curtis Manning -- were each overheard once in separate conversations during "foreign intelligence national security electronic surveillance," according to an affidavit filed by Attorney General William French Smith.

Smith said in the Oct. 6 affidavit that disclosing the contents of the conversations would "harm the national security of the United States."

The surveillance, which could have either been telephone wiretaps or room bugs, was approved by the special Foreign Intelligence Surveillance Court, a seven-member panel created by Congress in 1978 to review electronic surveillance requests by the FBI and the National Security Agency.

Officials would not say where the surveillance was conducted. They refused to say in response to a reporter's question whether it occurred at the Iranian interest section of Algerian Embassy, 2139 Wisconsin Ave. NW, which has housed Iranian government officials since their embassy was closed in 1979.

Rauf and Abdul-Mani were indicted with two others last summer after a federal grand jury concluded a year-long investigation of the July 1980 execution-style murder of Tabatabai, an outspoken critic of the regime of Iranian leader Ayatollah Ruhollah Khomeini. The indictment charged the suspects with conspiracy in the killing. It said cash payments were made but did not say who ordered or paid for the killing.

Assistant U.S. Attorney Robert W. Ogren has told Superior Court Judge Fred B. Ugast -- who will preside over the trial set to begin Nov. 2 -- that the government will not use the classified material in the trial.

Another man charged in the case, Khalid Al-Asad Abdul Raheem, also known as William Cafee Jr., was not overheard on the surveillance. No information was requested regarding the fourth defendant, accused triggerman Daoud Salahuddin, also known as David Belfield, who has fled the country and is believed to be in Tehran.

Under law, the government must provide the defense with any information that could help the defense's case. If a dispute arises over what material should be turned over, the judge can make a determination after privately inspecting the material. Where classified information is involved, the government must also ask a federal judge to inspect the material and determine whether it was legally collected as foreign intelligence and thus not subject to disclosure.

Earlier this month, the U.S. Attorney's Office here did ask a federal judge -- U.S. District Judge Oliver Gasch -- to make such a determination. He has not yet ruled. Now Ugast, the trial judge in the case, has also been provided the classified material and will be asked to examine it to see if any of it would benefit the defense.

Defense attorneys Thomas Abbenante and Bruce B. McHale claim that because the conversations likely were overheard as part of the criminal investigation into Tabatabai's death, and not during foreign intelligence gathering, the material should be disclosed.