BEAVERTON, Ore., Jan. 12 — Starting Saturday, January 15, television viewers will see a Nike (NYSE: NKE) commercial unlike any they’ve seen before. In fact, they’ll get to choose the ending … on the Internet.

Creating the illusion that the viewer is actually in the ad, the campaign will feature three world class athletes — world champion sprinter Marion Jones, baseball slugger Mark McGwire and snowboarding champ Rob Kingwill. In a classic cliffhanger theme, acclaimed music video director Johan Renck fades the ad to black just as the action heats up and a message directs viewers to whatever.nike.com. What has traditionally been a 30-second ad experience turns into a 20-minute interactive experience with the brand.

Created by long-time Nike ad agency Wieden & Kennedy, the new campaign supports the launch of Nike’s revolutionary new cross training shoe, the Air Cross Trainer II.

“This campaign is like nothing we’ve done before,” said Mike Wilskey, vice president of US Marketing. “It represents an unprecedented step for Nike, as we have integrated ‘traditional’ television advertising with the Internet, creating a unique and entertaining experience.”

In the first of the three ads, which debuts during the NFL playoffs on January 15, Jones challenges the viewer to a foot race through the streets and alleyways of Santa Monica while people, dogs and glass doors fly by. As Jones dashes down the beach promenade, dodging street performers and tourists, the viewer (in hot pursuit) slams into a man juggling chainsaws. When the roaring saws fall back to earth, the screen goes dark with a note telling viewers, “Continued at whatever.nike.com.”

NOTE: Some networks won’t allow “continued at” and will only show the URL address.

To resolve the cliffhanger, viewers must trade their remote for a mouse. At whatever.nike.com they will be able to choose from up to seven different endings for the unfinished TV ad using Apple’s QuickTime streaming media technology. From a disarming experience with the chainsaw to a boxing match or a spirited game of one-on-one basketball against “the world’s fastest woman,” the Web site will provide viewers/surfers with a chance to find the ending they like best.

For anyone who visits the Web site without seeing the ad on television, it will be digitized and available on the site, along with more information about Nike cross-training and the Air Cross Trainer II. New television ads featuring McGwire and snowboarder Kingwill will debut over the coming weeks, ending in cliffhangers resolved on the “whatever” site.