NEW YORK – The word “tentpole” is used to describe a blockbuster movie that can appeal to everyone. If it were applied to a festival, the Tribeca Film Festival would be it.

The sixth annual festival opens Wednesday with a wide selection of international art house fare, populist premieres and family friendly films – 157 features and 88 shorts jammed into 12 days of screenings, panel discussions and parties.

Since being founded in response to the Sept. 11 attacks by Robert De Niro, his producing partner, Jane Rosenthal, and her husband, the entrepreneur Craig Hatkoff, the Tribeca festival has gradually developed an identity as diverse as the city itself.

“We’re showing everything from an avant garde film called `Passio’ with live music by Arvo Part at the Cathedral of St. John the Divine – to `Spider–Man 3,'” said chief festival programmer and executive director Peter Scarlet.

“You can’t get two things that are more unlike each other, but it’s that almost surreal juxtaposition of different kinds of things that I think is an example of how we’re trying to redefine what a film festival is.”

Tribeca was launched in 2002, as Rosenthal says, because of an “act of war.” She and De Niro wanted to do something to benefit their neighborhood, just north of where the World Trade Center towers once stood.

They began with no long-term plans, but six years later, the festival has become an international fixture – nestled between the more domestic Sundance Film Festival in January and the pre-eminent international fest, Cannes, in mid–May.

Because of its origins, Tribeca will always be defined by its connection to Sept. 11 and the continuing reverberations of that tragedy.

“We are a political festival,” said Rosenthal in a recent interview in her Tribeca office.

Though Tribeca in its early years intentionally opened with heartwarming comedies like “About a Boy,” last year it confronted its history by opening with “United 93,” the documentary-like recounting of the flight that crashed in Pennsylvania on Sept. 11.

The festival has increasingly highlighted films that deal with post-Sept.11 issues like the Iraq and Afghanistan wars. That mission expands this year with a series of global warming-themed short films produced by the SOS (Save Our Selves) campaign. They will open the festival in a gala hosted by Al Gore on Wednesday.

“We will do things and show things and whether you like it or not, it’s something to see and it’s ways to ask questions,” said Rosenthal. “We might be able to do something about climate change quicker than we can do something about our current administration.”

Among this year’s political documentaries are “Taxi to the Dark Side” by Alex Gibney (“Enron: The Smartest Guys in the Room”), which details the policies behind the Abu Ghraib scandal; “Beyond Belief,” about two Sept. 11 widows traveling to Afghanistan; and “I Am an American Soldier: One Year in Iraq in the 101st Airborne,” for which filmmaker John Laurence documented soldiers’ lives for 14 months.

Among the big-tent events are the U.S. premiere of “Spider-Man 3” on April 30; the premiere of Curtis Hanson’s romance “Lucky You,” starring Eric Bana and Drew Barrymore; and one of the festival’s signature events: the Tribeca Drive-in.

“It’s really a sit-in,” joked Rosenthal, explaining that the outdoor screenings are her favorite part of the festival. This year will feature a 20th anniversary screening of “Dirty Dancing,” the animated “Surf’s Up” and “Planet B-Boy,” a documentary about breakdancing.

A new addition this year also pays respect to a genre often given scant attention at movie festivals: the sports movie. Sponsored by ESPN, Tribeca will present 14 premieres of sports-related films, as well as a screening of the baseball classic “The Natural.”

Serving as ambassadors of the sports festival are former NFL running back and now TV personality Tiki Barber, and tennis legend Billie Jean King.

Movies playing in the Tribeca Family Festival include “Gumby: The Movie” and a documentary on student council races in four different middle schools entitled “The Third Monday in October.”

A festival’s merit is often measured in its ability to present movies appealing to distributors – it’s a marketplace. The two most successful Tribeca-showcased films are “Transamerica,” which went on to yield Felicity Huffman a best actress Academy Award nomination, and “Jesus Camp,” which received an Oscar nomination this year for best documentary.

“I’d like to see a narrative picture break out in a mainstream way, but that takes time,” said Rosenthal. “You can’t do anything about it.”

Predicting what will catch on this year is impossible, but among the eagerly awaited films are the Leonardo DiCaprio-produced “Gardener of Eden”; the poker mockumentary “The Grand”; and “Lady Chatterley,” an adaptation of the second version (of three) of D.H. Lawrence’s erotic novel. The film won five Cesar Awards, the French equivalent of the Oscars.

But there are many more, from 47 countries and territories. Among the international entries are the Turkish “Times and Winds,” the Kurdish “Half Moon” and “The Last Man,” hyped as the first Lebanese vampire movie.

The festival can similarly boast the first movie directed by Fred Durst, frontman of rock-rap group Limp Bizkit: “The Education of Charlie Banks.” It’s surely a sign that at Tribeca, everyone is welcome.