An attorney for accused spy Jerry Alfred Whitworth acknowledged today that the retired Navy communications expert wrote a series of anonymous letters to the FBI in 1984 admitting his participation in a Soviet espionage ring.

But the lawyer, James Larson, contended in his closing argument that Whitworth did not suspect until late in his involvement in the spy ring that was headed by confessed spy John Anthony Walker Jr. that the material was going to the Soviet Union. Whitworth stopped supplying the material after learning that, Larson said.

Assistant U.S. Attorney William S. Farmer, calling Larson's argument a "Fantasy Island version of what really happened," told the jury that with such "amazing concessions . . . your job should be very easy."

The jury is to be instructed Friday, then start deliberations.

Larson said Whitworth initially believed that Walker was passing the classified material to Israel. "His state of mind was that he was aiding an ally which was under siege and losing the support of the U.S. government, which it deserved," he said.

Larson said that Whitworth never knew precisely that the Soviet Union was Walker's buyer, but that his suspicions led him to that conclusion. However, he said, "that conclusion didn't come until after Mr. Whitworth had stopped supplying any information to Mr. Walker whatsoever."

In the letters to the FBI, an individual who identified himself only as "RUS" said he did not realize that the highly sensitive coding information he was supplying to his contact was going to the Soviet Union "until after I had been involved a few years, and since then I've been remorseful and wished to be free."

"I'm not going to quibble with you," Larson told the jury. "The writer of the RUS letters was Jerry Whitworth."

Larson's acknowledgement that Whitworth wrote the RUS letters was perhaps the most damaging evidence against Whitworth other than Walker's testimony against his former Navy colleague. It represented a dramatic turnabout from the defense's previous contention that the government had not presented adequate proof that Whitworth was the author.

Larson acknowledged Wednesday that "there's absolutely no question" that Whitworth "received money, and a lot of it" for passing classified information. Today's statement added the fact that at a certain point Whitworth knew Walker's buyer was the Soviet Union, leaving open only the question of whether Whitworth participated in the spy ring after realizing that.

That point is crucial because U.S. District Judge John P. Vukasin Jr. has told prosecutors they must prove that Whitworth, in passing the classified material, intended to aid the Soviet Union or harm the United States

Whitworth, 46, is charged with 13 counts of espionage and federal income tax violations. He is accused of passing Walker copies of Navy codes and design manuals for coding machines that would have permitted the Soviets to read Navy communications.

Farmer, who described the Walker ring as "the biggest hemorrhage in the history of this country's military secrets," urged the jury to "put the label of traitor on Jerry Whitworth's forehead where it belongs -- 13 times," referring to each of the counts in the indictment