Morton Sobell, who was convicted in the Cold War spy trial that delivered Julius and Ethel Rosenberg to their deaths and divided the nation for decades, died on Dec. 26 in Manhattan, his son, Mark, confirmed on Wednesday. He was 101.

Mr. Sobell, whose death was not reported at the time, had lived in the Bronx and then on the Upper West Side and had recently been in a nursing home.

Serving 18 years in prison until 1969, Mr. Sobell asserted his innocence until 2008, when, in an interview with The New York Times, he startled his defenders by reversing himself and admitting that he had indeed been a Soviet spy.

“Yeah, yeah, yeah, call it that,” he said. “I never thought of it as that in those terms.”

In the interview, he also implicated Mr. Rosenberg in a conspiracy that supplied the Soviets with non-atomic military and industrial secrets stolen from the United States government.