washington | It’s a classified leak case that could rattle U.S. foreign policy and fundamentally alter how Washington does business. But while the world watches the implosion in the vice president’s office, this case is proceeding quietly across the Potomac.

Motions filed in recent weeks in the case against two former senior staffers of the American Israel Public Affairs Committee have gone virtually unnoticed in the mainstream media, but their implications could be as explosive as the perjury indictment last week against Lewis Libby, Vice President Cheney’s chief of staff and one of the architects of the Iraq war.

Defense motions suggest that the trial, now scheduled to start April 25, could expose the extent of covert U.S. surveillance of an ally, Israel, and how Israeli diplomats gather information about the United States.

It also could shed light on how journalists use intermediaries like AIPAC to gather information on how U.S. officials selectively leak information to manipulate public perception of U.S. policy, and on the inner workings of AIPAC, an organization famed for its media-shy profile.

At a hearing last week on pre-trial motions in the case charging Steve Rosen, AIPAC’s former foreign policy chief, and Keith Weissman, its former Iran analyst, with illegally transmitting classified information, U.S. District Court Judge T.S. Ellis determined that prosecutors may withhold evidence from the defense. Ellis said prosecutors persuaded him that it was in the national interest to do so.

Should Ellis eventually allow the publication of a substantial portion of the classified information, it could expose the breadth of covert attention that U.S. agencies pay to Israel and to AIPAC, a respected domestic lobbying organization. The prosecution hopes to stymie that exposure with its own motion that seeks not only to suppress most of the tapped conversations, but even their quantity. Ellis did not indicate whether he would suppress information about the quantity.

The defense may use the argument that Rosen and Weissman’s practices were routine. This notion got unexpected support last week from none other than Patrick Fitzgerald, the U.S. attorney who won the perjury indictment against Libby.

In an extended news conference, Fitzgerald sought to explain why he was prosecuting a coverup — the alleged perjury — and not the underlying alleged crime, the leaking of Valerie Wilson’s name.

“That would violate the statute known as Section 793, which is the Espionage Act,” Fitzgerald said. “That is a difficult statute to interpret. It’s a statute you ought to carefully apply. I think there are people out there who would argue that you would never use that to prosecute the transmission of classified information, because they think that would convert that statute into what is in England the Official Secrets Act.”

Indeed, Section 793 rarely is used to prosecute the transmission of classified information. Experts can’t think of a single case since the mid 1980s — until this year, when it was used to charge Rosen and Weissman.