The U.S. Postal Service, often derided by techies as "snail mail," pulled a Y2K stunt yesterday to cast itself as a quick and nimble letter carrier able to span the centuries. But, like the computer bug, the event had a few glitches.

White House presidential adviser John A. Koskinen had just begun a briefing on year 2000 computer glitches here and abroad when a man in a black tuxedo barged onto the podium, saying, "Package for Mr. Koskinen."

The carrier handed Koskinen a U.S. Postal Service "Express Mail" package postmarked early Friday morning in San Francisco and guaranteed for noon Saturday delivery in Washington.

Koskinen, who was sleep-deprived after a long night--and morning--at the White House's $50 million Y2K command center, fumbled his lines. "This is an actual FedEx package . . . from Los Angeles," he said, inadvertently giving a plug to a Postal Service rival.

He also prefaced his remarks by saying the delivery "looks staged"--and he was mostly right.

The package, containing "Celebrate the Century" stamps, did not come from any ordinary citizen, but the postmaster of San Francisco. The package also did not carry a street address, just Koskinen's name, title and organization. But the package did contain a nine-digit zip code.

The person in the tuxedo, who had waited out on the street in order to whisk the package past security guards and to the briefing room, was Jon Leonard, the Postal Service's Y2K communications manager.

Postal Service spokeswoman Beverly Burge said the holiday delivery was "a great way to show the system was working before, during and after the date change."

The package's 2,800-mile trip involved not only postal computers but coordinated handoffs to truckers and the commercial jetliner that carried mail between the two coasts, she said.

"It's one of the first pieces of mail delivered in the new millennium," Burge said.

Koskinen elicited chuckles from reporters when he concluded, "Now the question is, would we have told you if it didn't arrive? And we'll leave that to others to determine."