As a trial nears for two pro-Israel lobbyists accused of conspiring to obtain classified information, the war of words is escalating between lawyers for the two men and federal prosecutors.

Defense attorneys for the two former employees of the American Israel Public Affairs Committee, Steven Rosen and Keith Weissman, have accused an FBI agent involved in the case of lying in order to trick the men into incriminating themselves. Prosecutors contend the men understood exactly what the investigation was about and moved quickly to coordinate their stories.

In a motion filed last month, defense lawyers asked the federal judge overseeing the case, Thomas Ellis III of Alexandria, Va., to declare inadmissible the statements Messrs. Rosen and Weissman made to the FBI.

New court filings by prosecutors indicate that the two Aipac staffers were being already being regularly wiretapped when they were first approached by FBI agents. According to court papers, the agents said they were simply conducting a background investigation on a Defense Department analyst, Lawrence Franklin. In a telephone conversation on August 3, 2004, Mr. Rosen seemed suspicious that there might be something more to the inquiry, because background checks are usually done by other agencies and government contractors.

“Normally, I don’t think it’s done by the FBI,” Mr. Rosen said. “Is this a criminal matter?”

“No,” the FBI agent on the phone, Catherine Hanna, replied.

According to FBI reports on their initial interviews, Messrs. Rosen and Weissman both flatly denied that they ever received any classified information from Franklin.

Just before 8 a.m. on August 27, 2004, the FBI agents turned up the heat. Agents visited Mr. Rosen’s home in Silver Spring, Md. and made clear, according to their report, that this was a “serious national security investigation.” Mr. Rosen again denied receiving any classified information from Franklin.

“Rosen was informed the FBI was looking into Franklin for a long time and that the FBI knew he met with an Israeli official in the last several weeks. The FBI knew Franklin provided classified information to the Israeli official. The Israeli official indicated he already had the information and it was provided by Aipac,” the report said. Mr. Rosen is said to have denied knowledge of the episode and asked to contact an attorney.

On the same day, agents confronted Mr. Weissman at his home in Bethesda, Md. with an audio recording they said captured Messrs. Weissman and Franklin discussing “highly classified agency information.” Mr. Weissman is said to have denied that it was his voice on the tape and repeatedly answered, “I don’t know,” to the agents’ questions about the conversation.

The attorney for Mr. Weissman, John Nassikas III, and the lawyer for Mr. Rosen, Abbe Lowell, declined to comment for this article. For reasons that are unclear, their filing seeking to suppress the statements to the agents is under seal, but the government’s opposition, which includes details of the conversations, is part the public court record.

Prosecutors argued that Messrs. Weissman and Rosen, who both hold doctorates, could not have been easily deceived.

Indeed, the prosecution notes that wiretaps captured the two lobbyists, who were later fired by Aipac, comparing notes on their contacts with the FBI. Mr.Weissman rejected Mr. Rosen’s suggestion that this might be a simple background check. “That wasn’t what the guy wanted from me,” Mr. Weissman said. He said his wife suggested a third party, such as an Aipac attorney, be present during interviews with the FBI, but Mr. Rosen disagreed.

“I’m reluctant to act all defensive in a situation where we have no particular reason … It makes it seem as if we as an organization are involved in nefarious things,” Mr. Rosen said according to quotes in the government motion.

While the court papers make clear that the Aipac officials and others involved in the case were under extensive surveillance, the full context of the alleged statements was deleted from the public court files.

The trial in the case is set for August, but Judge Ellis is still considering a defense motion to dismiss the case on constitutional grounds.