NEW YORK -- Two companies backing an experimental impotence drug will become NFL sponsors, the league said Wednesday.

The deal is expected to be the beginning of a ferocious marketing war in territory Viagra currently has to itself.

Bayer Pharmaceuticals Corp. and GlaxoSmithKline, which expect their drug Levitra to be approved by the Food and Drug Administration later this year, wouldn't say how much they are spending on the three-year sponsorship. They also declined to disclose details of the agreement.

Published reports said the companies are spending $18 million. A source close to the deal who spoke on condition of anonymity said that figure was close to the actual amount of the deal.

Each week, 120 million people watch the NFL.

"This is a strategic opportunity for us. We will educate men on health issues," Bayer spokeswoman Nancy Bryan said. "Sexual health is a key issue."

Eli Lilly & Co. and Icos Corp., also are expecting approval later this year for their impotence drug, Cialis.

Currently, the impotence drug market is controlled by Pfizer's Viagra. In 2001, Pfizer spent $101 million marketing Viagra, making it the fourth most heavily promoted drug in the country that year -- and that was when it had the market all to itself.

"`We expect Pfizer will continue to market its product," said Glaxo spokesman Michael Fleming. "But we have a robust and exciting campaign."

He said specifics of the campaign would be released in the coming weeks.