LONDON — Broadcasters are already seeing a drop in advertising revenue for NFL games because of the global economic crisis, league commissioner Roger Goodell said Friday.

At a conference on the globalization of sports held ahead of Sunday's NFL game in London, Goodell also reiterated that the league will face challenges in the current economic climate, but that the NFL is "incredibly strong" and should weather the downturn relatively unscathed.

However, he said network partners are already reporting that advertisers are pulling back, both on a local and national level.

"The sales market is different than it was even several weeks ago," Goodell said during a panel discussion with Richard Scudamore, the chief executive of the English Premier League. "We see it primarily on a local level, which I think is through a large extent a reflection of what is happening in the automobile industry. But it has now in the recent weeks gone to the national level. It's had an impact. The fortunate thing is that it hasn't had an impact on our viewership."

Goodell did not give any specific figures for the advertising drop, and was not available for media interviews after the discussion, which was moderated by CBS announcer Jim Nantz.

Goodell said he was confident that ad sales for the games would stabilize even in the short term, adding that holding onto sponsors would be a bigger long-term problem for the league.

"That's something we are evaluating, whether there will be a long-term change in the way companies invest in sponsorships, and how they do that," he said. "And that could impact us well beyond 2009."

But even with all professional sports already feeling the squeeze of the credit crunch, Goodell was confident that the NFL's products should stay in high demand.

"It's hard to see that people are going to give up quality in a time like this," he said. "I think we are the ones who have the potential to come through it the strongest if we're intelligent about it."

The NFL is staging its second game at Wembley on Sunday, when the New Orleans Saints face the San Diego Chargers. The game is a way for the NFL to continue its growth abroad. The NBA and NHL have also staged games in Europe over the last two years.

But with the Premier League already established as one of the most popular in the world, Scudamore said he didn't feel threatened that American sports would take away revenue from football.

"I don't see really that we're competing," Scudamore said. "I think it's an awfully big pond out there that we all fish in."