SAN FRANCISCO — Pearl Jam, the nation's most popular rock group, abruptly canceled its U.S. tour Saturday, moments after a concert here during which singer Eddie Vedder left the stage ill.

After singing seven songs with the intensity that has made him one of the most commanding rock performers in years, Vedder stunned the crowd of 50,000 at Golden Gate Park by announcing that he couldn't continue with the performance.

"I think that might be it for me for a while," he said, explaining he had been so sick from stomach flu that he had gone to the emergency hospital at 3 that morning.

"Lucky for you," he said before leaving the stage. "Neil Young is here."

Young, who recently recorded a new album with Pearl Jam, was waiting backstage to play some of the songs from the album during the band's encore.

After Vedder's remarks, Young huddled with the other members of the Seattle quintet and led them back on stage for an inspired, two-hour set that included six songs from the new "Mirror Ball" album, which will be released Tuesday.

The cancellation of the remaining seven cities on the brief U.S. tour, which began June 16 in Casper, Wyo., was decided in a backstage meeting between the four other band members and manager Kelly Curtis. The band's next concerts were to have been tonight and Tuesday at the San Diego Sports Arena. Refund information is expected to be announced shortly.

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Though none of the meeting participants was available for comment Sunday, a source close to the band said that the four other group members--bassist Jeff Ament, guitarists Stone Gossard and Mike McCready and drummer Jack Irons--canceled the shows because the "pressures of a full-scale tour simply took the joy out of making music" and, more significant, they feared "those pressures would ultimately destroy the band if not dealt with."

Those pressures of touring are believed to be felt particularly by Vedder, whose most compelling songs reflect the alienation and anger of his troubled youth.

After Vedder's remarks about a hospital visit Saturday, rumors spread that he had suffered a drug overdose, but both Vedder and people who work with Pearl Jam have repeatedly insisted that he does not have a drug problem.

The singer has spoken repeatedly in interviews about the difficulties he has had in adjusting to stardom--anxieties similar to those expressed by Kurt Cobain, the leader of Nirvana who committed suicide last year.