Attorney General Janet Reno faulted Justice Department and FBI subordinates yesterday for not coming to her two years ago with their disagreement over whether to wiretap a nuclear weapons scientist suspected of spying for China.

"Where there is something serious, where [FBI] Director [Louis J.] Freeh disagrees with the findings [of Justice Department officials], I think that it should be discussed at my level," Reno told her weekly news conference. "I was not briefed on the details."

Reno delivered her most detailed explanation yet of how the Justice Department handled allegations that Wen Ho Lee, a Taiwanese-born scientist at the Los Alamos National Laboratory, may have given nuclear weapons secrets to China.

Reno's comments came after aides pleaded with her to rebut suggestions from Sen. Richard C. Shelby (R-Ala.), the intelligence committee chairman, and Sen. Robert G. Torricelli (D-N.J.), usually a staunch defender of the Clinton administration, that she should resign or consider doing so.

Reno explained that when the FBI first sought in 1997 to wiretap Lee, the warrant application was rejected. The FBI then reworked the application twice to add information, but it was still rejected.

"Based on the facts reported to us in 1997, the department determined that the evidence was insufficient to support a finding of probable cause" to believe Lee engaged in clandestine intelligence-gathering on behalf of a foreign power, which is the standard for seeking a warrant in national security cases, Reno said.

Reno said then-Assistant FBI Director John Lewis complained about that decision to her without going into details, so she asked for a further high-level review and the warrant application was rejected again.

"I assumed since I did not hear again from the FBI that it was resolved to their satisfaction," Reno said. Looking back now at the evidence available in 1997, the career lawyers were correct to reject the wiretap, Reno said.

The FBI did not contest the decision further but instead investigated Lee by other means, according to a senior bureau official. Lee, who denies spying, was fired this spring and remains under investigation.