WEST HOLLYWOOD - There is a lot at stake with "Green Lantern" - at least for its star, Ryan Reynolds, and Warner Brothers.

Until now Mr. Reynolds, 34, has been best known for light roles in romantic comedies like "Definitely, Maybe" and "The Proposal." Hollywood's leading-man club has been harder to crack. Mr. Reynolds had a supporting role in "X-Men Origins: Wolverine," but an effort last year to build an entire film around him, the thriller "Buried," flopped. His most successful title role arguably remains "Van Wilder," a 2002 comedy.

"Green Lantern," which opens worldwide this summer, is this Canadian actor's full-bore effort to prove that he can anchor a summer blockbuster. And he must do it while wearing a silly mask and tights, and saying lines like: "Let those who worship evil's might beware my power."

"Oh, man, was I nervous about it," Mr. Reynolds said during a recent interview at the Sunset Tower Hotel here, adding that the pajamalike motion-capture suit he wore for much of the shoot was not exactly calming. "You want me to do what? And I'm supposed to do it in crash-test jammies?"

Warner is nervous too. Just as "Green Lantern" is an effort by Mr. Reynolds to redefine his career, the picture represents a bid by the studio to create a superhero franchise beyond Batman and Superman. Although they are both huge multiplex forces, with sequels forthcoming, Warner has tried and failed for years to bring the likes of Wonder Woman, the Flash, Justice League and Green Lantern to the screen. (Let's not even bring up "Catwoman.")

All the while Marvel Entertainment, now owned by the Walt Disney Company, has catapulted one comic book character after another onto the big screen, most impressively the lesser-known Iron Man, and now Thor.

"Green Lantern" is Warner's first superhero release since making management changes at DC last year and more deeply integrating it into the studio's development machinery.

The pressure is intense not only because of the Marvel rivalry: the Harry Potter franchise ends in July, and Warner's plan for replacing those riches turns squarely on DC characters.

And although fans now seem receptive to the $300 million "Lantern," an early trailer was poorly received.

"There is a lot at stake," said Jeff Robinov, Warner's top movie executive. But, he said, said "Batman Begins" "did about $370 million worldwide" and spawned a sequel," "The Dark Knight," which earned more than $1 billion at the global box office, plus DVD money.

"Green Lantern," which was directed by Martin Campbell ("Casino Royale"), is a space extravaganza. Mr. Reynolds plays Hal Jordan, a new recruit to the Green Lantern Corps, a type of secret police for the universe. Hal must master his new powers conferred by the corps' magic ring while pining for his Earthbound love interest (Blake Lively). He eventually fights the villain, Parallax, who is aided by Peter Sarsgaard ("An Education").

The plot springs directly from Green Lantern comics, which started in 1940 after a cartoonist saw a subway man wave a green lantern as an all-clear signal.

Warner is playing up the film's vastness as a way to stand out; a cool costume and a swarm of computer-generated effects may not fill theaters anymore.

"Green Lantern" producers say Mr. Reynolds (who is divorced from the actress Scarlett Johansson) is a Hollywood rarity: a star who appeals to both sexes.

In the hotel, Mr. Reynolds was funny and fully aware of his perennial high ranking on People magazine's sexiest men alive lists. Yet he was also humble (he drove himself to the interview).

"We knew immediately that we put the ring on the right finger," said Donald De Line, a "Green Lantern" producer. A sequel is already deep in development.

Even so, the studio considered other names, including Chris Hemsworth, who went on to star in "Thor."

Mr. Reynolds, who has a number of upcoming films, displays a self-deprecating sense of humor.

"I'm just glad they didn't ask me to play 'Wonder Woman,'�? he said. "On the other hand, that could be fun. The short shorts. The tall boots. What do you think?"

As with any superhero movie, he said, the challenge is taking the story line seriously while signaling that the film gets the joke. Near the end of "Green Lantern," as Mr. Reynolds and Ms. Lively start to kiss, she blurts out, "What the hell is with that mask?"

He shrugs - the petite eye covering looked ridiculous, sure, but Hal Jordan wasn't built to fear embarrassment.

His response: "Came with the outfit."

The New York Times