WASHINGTON, May 21 - A former senior officer in a pro-Israel lobbying group who was fired because of his involvement in an espionage case says that he did nothing wrong and that he does not understand why he is the subject of a criminal investigation.
"I did not violate any U.S. laws," said the former officer, Steve Rosen, who is at the center of the swirling counterintelligence investigation. Mr. Rosen was a well-connected senior policy analyst and lobbyist for the group, the American Israel Public Affairs Committee, until he was fired last month.
Leaders of other major Jewish organizations - some who are close to Aipac, as the organization is known, and others who are not - say they believe that Mr. Rosen and a colleague, Keith Weissman, were fired to insulate the group from criticism ahead of its annual convention, which opens on Sunday. Aipac denies that.
Mr. Rosen and Mr. Weissman were fired because of their association with Lawrence A. Franklin, a former Pentagon analyst who was arrested on May 4 on charges of illegally disclosing military secrets.
No charges have been filed against the two, and the organization has not been implicated in the investigation, law enforcement officials said. Many senior government officials, including Secretary of State Condoleezza Rice and the House speaker, J. Dennis Hastert, are scheduled to attend the convention, as is Prime Minister Ariel Sharon of Israel. None of the major officials have canceled their plans to attend.
Aipac has long been an important organization to the government; officials strive to keep close relationships with it.
Even with the two former Aipac officials under federal investigation, support for Aipac among other Jewish groups remains strong.
Still, there is little question that the organization's lobbying arm has been damaged by the loss of Mr. Rosen and Mr. Weissman, and the broader espionage accusations may discourage some government officials from dealing with Aipac. Mr. Rosen and Mr. Weissman often spoke with colleagues in the Israeli Embassy, and as part of their work traded information with the Israelis.
"Some middle-level people in government will be hesitant" to talk to Aipac now, said Malcolm I. Hoenlein, executive vice chairman of the Conference of Presidents of Major American Jewish Organizations, an umbrella group whose members include Aipac. He and others suggested that some government officials might fear that they, too, could be swept up in an espionage case.
Patrick Dorton, a spokesman for Aipac, said that the organization "continues to have meetings and exchanges at all levels of government."
Morris J. Amitay, a former executive director of Aipac, voiced another concern shared by almost everyone interviewed: "the risk," he said, "that the Department of Justice comes up with something that could be incriminating to Aipac."
Over several years one or both of the Aipac lobbyists held four meetings with Mr. Franklin, who was under surveillance by Justice Department investigators. When Mr. Rosen and Mr. Weissman began meeting him, they too were under surveillance. During a final meeting between Mr. Franklin and Mr. Weissman in July 2004, Mr. Franklin was serving as a government informant, and the meeting was taped.
The people sympathetic to Mr. Rosen's case said they regarded the meeting as a sting because Mr. Franklin described information about threats to Israeli operatives who were working in northern and southern Iraq. Iranian agents, Mr. Franklin said, planned to kill them.
Mr. Weissman told Mr. Rosen about this, the people said, and the two set out to confirm what Mr. Franklin had said by talking to American and Israeli officials.
Soon after, an F.B.I. agent questioned the two and asked if they had spread classified information. They said no and maintained in discussions with the agent and with Aipac officers that Mr. Weissman never heard Mr. Franklin say the material he was describing was classified.
Later, lawyers learned that the tape of Mr. Franklin's last conversation with Mr. Weissman showed that he did note that the information was classified. After learning that, Aipac fired Mr. Rosen and Mr. Weissman, said several friends of Aipac who were briefed on the investigation.