NEW YORK, FEB. 16 -- The late Roy Cohn claimed in his autobiography that the judge in the Rosenberg spy case decided before the trial that he would put Julius Rosenberg to death, according to an excerpt published today.

Cohn, who was the prosecutor in the 1951 case, also asserted that U.S. District Judge Irving R. Kaufman often telephoned him during the trial to seek his advice on a penalty for Ethel Rosenberg. Cohn said he recommended the death penalty for Ethel Rosenberg. She and her husband were convicted of selling atomic secrets to the Soviet Union and were executed in 1953.

Kaufman, who remains on the bench, could not be reached for comment. "The judge is not available, and it's the policy of the chambers not to comment on press reports," a law clerk said.

Excerpts from Cohn's forthcoming autobiography, which was written with journalist Sidney Zion, were published in the current issue of New York magazine. Cohn, a controversial figure who was also known as the chief counsel to Sen. Joseph McCarthy in the 1950s, died in August 1986 of cardiac arrest, with AIDS-related infections listed as secondary causes. During a stormy career that included bitter run-ins with the Internal Revenue Service and many public figures, Cohn's veracity was frequently challenged.

In the book, Cohn recalled that Kaufman had said that he sought divine guidance in his synagogue before deciding on the sentences. "I can't confirm or deny this. So far as I know, the closest he got to prayer was the phone booth next to the Park Avenue Synagogue. He called from that booth to a phone behind the bench in the courtroom, to ask my advice on whether he ought to give the death penalty to Ethel Rosenberg ... There was never any question about Julius: Kaufman had told me before the trial started that he was going to sentence Julius Rosenberg to death."