Jay Leno's closely watched new prime-time TV show drew a bumper audience of nearly 18 million viewers, cheering executives at struggling NBC on Tuesday but leaving TV critics underwhelmed.

The debut of The Jay Leno Show at 10 p.m. on Monday beat the competition to become the No. 1 network show of the night and gave NBC its biggest overall audience in that time slot since the August 2008 Olympic Games, NBC said.

The 17.7 million viewers compare to the roughly 5 million that regularly watched Leno's old Tonight Show during late-night hours, and it put the new outing on par with popular shows like the CSI crime franchise on rival CBS.

Leno's move from his former 11:30 p.m. time period to the prime-time slot five nights-a-week that is traditionally occupied by expensive scripted drama is being scrutinized by the network TV industry as it struggles to cut costs and retain audiences.

General Electric Co's NBC network has been particularly hard hit and has been in last place for four years among the leading four networks.

NBC Universal Chief Executive Jeff Zucker told reporters on Tuesday the Leno debut was a very nice start but cautioned that it was early days yet.

We're going to judge this on 52 weeks, we're not going to judge it on one night. The fact that it opened and opened so well is a great sign, and we feel great about that. But it's only one day, said Zucker, attending an investment conference in New York.

NBC has declined to publicly reveal its target ratings for the show, which costs roughly the same for five nights as does one night of a scripted drama.

But the premiere, which featured appearances by comedian Jerry Seinfeld, rapper Kanye West and comedy skits involving talk-show host Oprah Winfrey and President Barack Obama, failed to wow critics.

Sixteen minutes into the new 'The Jay Leno Show' it was difficult not to panic. This is the future of television? This wasn't even a good rendition of television past, wrote Los Angeles Times TV critic Mary McNamara.

Alessandra Stanley of The New York Times said: So much ink has been devoted to describing how Mr. Leno's new show would depart from his old one that it was startling to see how little difference there was.

Time magazine's James Poniewozik, who last week wrote a cover story declaring NBC's radical experiment The Future of Television, said it ultimately did not matter whether critics liked the new show.

It cannot be overemphasized that Leno's show is first and foremost a cost-cutting move. It's a fifth or less expensive than airing scripted dramas; therefore, what would be a bad number for 'Law & Order' would still leave NBC in the black on Jay, Poniewozik wrote on Tuesday.

Rival studios have scorned NBC's experiment and loaded their upcoming fall schedules with dramas that traditionally deliver big audiences to advertisers that fund network TV.

But on Monday, Leno's only competition in the time slot was a repeat episode of CSI: Miami on CBS, and ABC's airing of the 2006 movie Dreamgirls.

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