By Ka Yan Ng

TORONTO (Reuters) - This year's Toronto International Film Festival will mark a return to relevant cinema, organizers said on Wednesday, but that's unlikely to dim the star wattage set to illuminate the September event.

Co-director Noah Cowan described the 2007 festival as a "watershed" moment, particularly for U.S. films set to be screened, which he said show "seriousness of purpose" and delve critically into American politics and the war in Iraq.

"If anything it recalls the great cinema of the 1970s," he said. "It feels like the cinema is relevant again."

Organizers said the festival will screen 349 films from 55 countries over 10 days next month.

Hollywood glitterati including Brad Pitt, George Clooney, Cate Blanchett, Reese Witherspoon, Sean Penn, and Jennifer Connelly are set to be in town for the festival, organizers said. They are among the more than 500 filmmakers, actors and industry insiders expected to attend.

Twenty films, chock full of Academy Award winners, make up the gala schedule.

Clooney stars in "Michael Clayton", about a "fixer" who does dirty work for a high-powered law firm.

"Rendition", starring Witherspoon, Jake Gyllenhaal and Meryl Streep, is about an American trying to track down her Egyptian-born husband, who is being held at a secret CIA detention facility.

Jonathan Demme's "Man from Plains", is a documentary on former U.S. President Jimmy Carter, while Brian De Palma's "Redacted" is a fictional take on a squad of American soldiers in Iraq. "Captain Mike Across America" looks at documentary director Michael Moore's activities during the 2004 U.S. presidential election.

Directed by Jeremy Podeswa, Canadian entry "Fugitive Pieces", which is based on the novel by Anne Michaels, will open the festival, which runs from Sept. 6-15.

The festival is now in its 32nd year and ranks with Cannes, Sundance, Berlin and Venice as one of the world's most influential. It has gained a reputation as the kick-off to the Hollywood awards season.