LOS ANGELES (Reuters) – U.S. gay activists are worried that comedian Sacha Baron Cohen's new film, "Bruno," could reinforce negative stereotypes about homosexuals just as they are making gains in the fight for rights such as same-sex marriage.

Cohen, who scored a surprise hit in 2006 with "Borat: Cultural Learnings of America for Make Benefit Glorious Nation of Kazakhstan," portrays a flamboyant gay Austrian fashion reporter in the new film that premieres on Wednesday in London and opens in the United States on July 10.

The studio releasing "Bruno" says the film's intent is to satirize homophobia, but some gay advocates are wary.

"We do feel the intentions of the filmmakers are in the right place -- satire of this form can unmask homophobia -- but at the same time it can heighten people's discomfort with our community," said Rashad Robinson, senior director of media programs for the Gay and Lesbian Alliance Against Defamation.

With that in mind, GLAAD asked in vain for Universal Pictures, the studio behind "Bruno," to add a message from Cohen addressing the importance of gay rights and tolerance.

Universal says in a statement it believes most moviegoers will understand the film's "positive intentions."

"'Bruno' uses provocative comedy to powerfully shed light on the absurdity of many kinds of intolerance and ignorance, including homophobia," the studio said.

The movie comes out as U.S. same-sex couples have won the right to wed in six states amid a fierce debate on gay marriage that has seen California voters approve a ban on such marriages.

HIT? OR MISS

"Bruno" is expected to be a hit, although there remains a big question about whether the young men who make up a core Hollywood audience will turn out for a movie about a gay man.

"It's going to be interesting to see if a bunch of teenage boys actually care to go", said gay activist Cathy Renna.

But one thing is certain -- Cohen has a huge fan base. Men and women flocked to "Borat," a fake documentary about a Kazakh journalist traveling across the United States that used comedy to expose bigotry. It earned $128 million at U.S. and Canadian box offices and $133 million in other countries.

Like its predecessor, "Bruno" is a mock documentary that covers the fashion reporter after he loses his job in Austria and goes to America looking to become a celebrity. Bruno wears mesh shirts, talks with a lisp and has a penchant for dropping his pants.

His unscripted encounters with everyday Americans and prominent figures, who think he is real, often devolve into people's disgusted reaction to Bruno's in-your-face sexuality.

In one scene, for instance, a martial arts teacher shows Bruno how to guard against gays. GLAAD's Robinson said another scene worried him that shows Bruno appearing to have sex with a man in a tub, while his adopted baby sits nearby.

"That wasn't really unmasking homophobia, and especially in a country where same-sex couples can still be denied the ability to adopt children that they've raised since birth. Trivializing gay families isn't a joke," Robinson said.

But gay groups also see potential from the film. "Bigotry and homophobia still today get cloaked in many different nuanced ways, so a movie like this has the potential to let everyone in on the joke and to really change the way homophobia is viewed," said Brad Luna, a spokesman for the Human Rights Campaign.

(Editing by Bob Tourtellotte and Peter Cooney)