The FBI investigation into whether a Pentagon analyst passed classified information to Israel is yet another political weight on Defense Secretary Donald Rumsfeld, still fending off criticism over the Iraq war and prisoner abuse.
It is not clear whether the investigation will result in charges of espionage at the Pentagon. At the least, the probe complicates Rumsfeld's position as congressional committees that oversee the Defense Department prepare for more hearings on the abuse scandal.
Rumsfeld has not commented publicly on the FBI's investigation. While the FBI has spent more than a year on the case, it only became public on Friday.
Officials, speaking on condition of anonymity, say the investigation is focused on Lawrence Franklin, an analyst of Iranian affairs who works in a policy office headed by Douglas Feith, the undersecretary for policy. Feith has been accused by Democrats of seeking to manipulate intelligence to help make the case for going to war in Iraq. Congressional investigations have found no evidence of that.
The New York Times reported on its Internet site in a story for Monday's editions that government officials say Franklin had been cooperating with federal agents for several weeks and was preparing to lead them to contacts inside the Israeli government when work of the investigation, first reported by CBS News, was leaked late last week.
The Israeli government has denied spying on the US.
Efforts to reach Franklin by telephone have been unsuccessful. Local law enforcement officers have kept reporters and photographers away from his secluded home in rural West Virginia, about a 90-minute commute from Washington.
The Washington Post reported on Sunday that the FBI investigation has broadened to include interviews with individuals at the State and Defense departments as well as Mideast affairs specialists outside the government. Israeli officials predicted that the allegation it got secret information on White House policy toward Iran from the Pentagon analyst would prove false.