A constitutional clash is looming in a Virginia courtroom after federal prosecutors proposed barring the public from hearing some evidence at the upcoming trial of two former lobbyists for the American Israel Public Affairs Committee. Defense lawyers for the two men, Steven Rosen and Keith Weissman, have objected vigorously to the unusual proposal to present secret evidence. Late yesterday afternoon, a consortium of news organizations filed a motion to intervene in the case to restrain any attempt by the government to give the jury access to evidence that the public will not be permitted to examine.

"If evidence is presented in this case, the public and the press should have the right to see it," an attorney for Mr. Weissman, John Nassikas III, told The New York Sun. "The government has made some proposals about how to handle government evidence that we believe would deny the public the right to see it and, in turn, deny the defendants right to a public trial." Mr. Nassikas said he could not elaborate because details of the government's proposal and of the defense's response are under seal, as are many other briefs filed in the case. The only public sign of the dispute in the court's docket is the title of a defense motion filed last week, which made mention of an effort to "strike the government's request to close the trial." A source familiar with the case said the government proposed giving jurors headphones to listen to audio recordings of intercepted and wiretapped phone conversations key to the case. While the defendants and the judge would be able to hear the audio, the press and public would not, the source said.

"It's a big deal," the executive director of the Reporters Committee, Lucy Dalglish, said. She said her group's initial research has found no case where the government was permitted to present extensive evidence that the public never saw.

Ms. Dalglish said the proposed secrecy is the latest troubling development in a case she already finds distressing. "I am not aware of anything as drastic as what I have heard has been mentioned in this case," she said. "This is a very important case in which two lobbyists are accused of violating the Espionage Act by taking information from a government source and turning it over to others, which is functionally not all that different from what reporters do every day. We think the media and the public has an unusually direct interest in how this trial is going to be conducted."

Messrs. Rosen and Weissman were fired by Aipac before being indicted in 2005 on charges that they conspired to pass classified information to an Israeli official and to reporters. The pair allegedly solicited and obtained information from a Defense Department analyst, Lawrence Franklin, who pleaded guilty and is cooperating with prosecutors.

The two former Aipac staffers have pleaded not guilty. They have argued that they had no duty to safeguard classified information since they were not government employees or contractors, but Judge Thomas Ellis III has rejected that position.

Attorneys not involved in the case said they were perplexed by some aspects of the government's proposal. It was unclear, for instance, what jurors would be told about the classified information, whether they would be sworn to secrecy for life, and whether they would be told of their obligations before the trial begins.

"I have a real problem with that," one defense lawyer, Eugene Fidell, said. "Jurors are not, in fact, privileged characters. They don't have security clearances. It sounds to me like we're going down the path towards secret trials, which we don't have."

Lawyers for the two ex-lobbyists are expected to argue that special warnings to the jury about keeping evidence in the case secret could undercut the pair's defense, which includes an argument that the information disclosed by the men did not represent a threat to America or a potential boon to a foreign government.

Defendants are guaranteed public trials in criminal cases by the Sixth Amendment to the Constitution. The Supreme Court also has held that the press and the public have a constitutional right to witness criminal proceedings.

The judge set a hearing for tomorrow on the government's secrecy proposal. An entry in the court's docket yesterday said the hearing also would be held in secret, at least for now. The trial in the case is tentatively set for June 4, but that date is in question after the judge suspended some legal deadlines related to the classified information to be introduced in the courtroom.

A spokesman for the prosecutors, James Rybicki, had no immediate comment yesterday. Mr. Rosen's attorney, Abbe Lowell, could not be reached.

Several New York-based groups that have objected to the use of secret evidence against terrorism suspects were silent yesterday about the developments in the Aipac case.