More than a half-century since he held the world heavyweight boxing championship, Jack Dempsey was remembered yesterday as one of the seminal figures of American sports, an athlete who transcended the limits of the ring to become a household word in the minds of generations of American sports fans.

Dead yesterday of natural causes at the age of 87 in New York, Dempsey was recalled by veteran trainer Ray Arcel as "one of the greatest fighters who ever lived, and one of the hardest punching heavyweights. He was only 180-185 pounds and he'd fight these big guys. He didn't care, flatten them in a round or two. He was a natural fighter and a very decent man."

Said retired U.S. District Court Judge John J. Sirica, who presided over the Watergate trials a decade ago and was a friend of Dempsey for nearly 50 years, "I think I've lost my best friend. He was just like a brother of mine."

Sirica, a fighter himself before he turned his talents to the legal profession, toured the country together with Dempsey to promote savings bonds drives toward the end of World War II, and when Sirica was married in 1952 Dempsey stood up for him as his best man.

"We were very close," said Sirica, who was told of Dempsey's death in a telephone call from the former champion's wife Deanna, according to The Associated Press.

Dempsey, heavyweight champion from 1919 to 1926, died at 5:05 p.m., according to a spokesman for the New York City medical examiner's office. The family said private funeral services were planned.

A prominent and visible figure at sports events for most of the half-century since his retirement from the ring, Dempsey had been in ill health in recent years, and he rarely left his apartment. Until 1974, he was frequently seen at the famous Broadway restaurant that bore his name, but he slipped further from the public after it closed.

Only 24 when he seized the heavyweight title from Jess Willard with a third round knockout in Toledo, Ohio, Dempsey held the crown for seven years until Gene Tunney stripped him of it in a 10-round decision in 1926.

Recalled the veteran trainer Arcel, "I first met him in 1920 right after he won the title. I knew him quite well. In 1925 I spent a lot of time with him. Unfortunately after he won the title, he engaged in too many exhibitions and stage work.

"Nobody can ever realize how much better he would have been as a fighter if he had just stuck with fighting instead of acting too. I liked him very much. I knew him, and we were very close in the early years."

From Dempsey's boyhood home in Manassa, Colo., Luther Bagwell, 93, the only resident remaining who lived there when Dempsey did, recalled Dempsey as "a good fighter even when he was a kid."

Bagwell, who knew Dempsey from birth to about the age of 16, said, "When we were kids that age, boxing was about the only amusement we had."

Dempsey's father worked as a laborer in the small, mountain community, Bagwell recalled. "It was a hard-up family. He had to go barefoot all during the summer like the rest of us kids did . . . "

Veteran fight publicist Irving Rudd called Dempsey "one of the giants of sports, a larger-than-life figure . . . He was a wonderful man. A giant star has fallen out of the heavens tonight. He was kindly, engaging and easily approachable . . . one of the most approachable men I've ever met."

Bert Sugar, the editor and publisher of Ring Magazine, said Dempsey "was perhaps the man who sculpted the golden age of sports . . . Sixty years later he was still the greatest, regardless of what Muhammad Ali says."

Irwin Rosee, former heavyweight champion Joe Louis' personal manager for many years, said he considered Dempsey and Louis the two greatest fighters of all time. Dempsey, he said, represented the "Golden Era of boxing."

"He was big and he represented power," Rosee told the Associated Press.

Jack Sharkey, a Depression era heavyweight champion who won the title from Max Schmeling in 1932, recalled a 1927 bout with Dempsey, the year after Dempsey lost his title.

"I turned to the referee to complain I was getting hit low, and I got hit with a haymaker. That was that. I was out on the canvas," said Sharkey, now 80, who was knocked out in the seventh round of his fight with Dempsey. Nevertheless, said Sharkey, he maintained his friendship with Dempsey years and visited him in New York about two months ago.

Eddie Futch, who broke into the boxing business in the 1930s and currently trains World Boxing Council heavyweight champion Larry Holmes, said Dempsey had a profound affect on fighters during the Depression.

"That era was influenced by Jack Dempsey's style. Dempsey was a bobber and weaver. The gyms were full of fighters who were bobbing and weaving like Jack Dempsey."