By Tom Brook New York

De Niro and Rosenthal co-founded the film festival in 2002

The Tribeca Film Festival got underway on Wednesday with the promise of a slew of films dealing with politics and other topical social issues.

Big name stars will also be in the spotlight during the 12-day festival, during which more than 150 films will be screened.

Former Vice President Al Gore launched the event in New York, introducing seven shorts on climate change put together by a number of well-known directors.

Bristol-based Aardman Animation has made one of them - and there are also contributions from two British directors, Jonathan Glazer and Kevin MacDonald.

The films can be seen as a rebuke to what many Bush administration critics claim is the US president's intransigence when it comes to effectively addressing global warming.

In addition to climate change, there are films that focus on Iraq, the US treatment of prisoners in Afghanistan and Guantanamo Bay.

We are a festival that started because of an act of war Jane Rosenthal

Tribeca's co-founders, Robert De Niro and Jane Rosenthal, say the festival's commitment to political films is connected to its origins - founded in the wake of the 11 September attacks which devastated the local neighbourhood.

"We are a festival that started because of an act of war," says Rosenthal, adding that "film-makers can sometimes break through with a message and point of view that politicians can't".

De Niro remembers the dark days following 11 September 2001, when he felt that a film festival was the only way to revitalise the neighbourhood where he lived.

The actor and director says: "It was grim - we had always talked about doing a festival, and just kicked it around, and somehow this seemed obviously the right time to do it - and that was it, we just jumped in."

Gore's An Inconvenient Truth won best documentary at the Oscars

But he doesn't want the festival to be seen as just a political showcase.

"It's political and it's a lot of things," says De Niro, who hopes it will be "all things to all people".

"I know it's impossible, but that's what we're trying - and some things will work and some things won't," he adds.

The festival aims to be a celebration of music and culture, with special events including street fairs and drive-in movie screenings.

This year, for the first time, there is also a series of sports films.

With Al Gore hosting the opening night gala, there may have been a groan from his critics who view it as a cynical effort to use an entertainment-related event to advance a political agenda.

But at Tribeca, Gore certainly has more supporters than detractors.

I'm not a figurehead. I feel very strongly about everything, and so in that way I'm very much part of it Robert De Niro on his Tribeca role

"Climate change is such a huge issue that you sometimes feel overwhelmed by it," says Rosenthal.

"The good news is that with all of these films, it gives you a good message about what you can do as an individual and what we can do to really change the world around us."

In its first five years the Tribeca festival has become a sprawling celebration, with screening venues in some cases several miles from its Ground Zero origins.

In the past there were complaints that there were too many films - and many journalists covering the festival found it lacked focus.

This year there has been a modest reduction in screenings. The films being presented run the gamut from edgy indie works and obscure non-English language pictures to mass-market populist fare.

The festival is even participating in a citywide promotional Spider-Man 3 week.

Tobey Maguire and Kirsten Dunst will arrive in New York for the film's US premiere, following an eight city international publicity tour.

Tobey Maguire reprises the superhero role in Spider-Man 3

Although Tribeca purists want to make sure the festival isn't hijacked by Hollywood, De Niro doesn't see the Spider-Man hoopla as a bad thing.

"Spider-Man helps raise awareness and helps the attention that the festival gets, so that's the good thing about it," he says.

De Niro enjoys a lot of respect for getting the festival off the ground and giving it momentum.

Questions have been raised over whether he is doing more than just lending his name, but he maintains that he works closely with Rosenthal.

"I'm there. I'm not a figurehead. I feel very strongly about everything, and so in that way I'm very much part of it."

Since 2002, the festival has attracted over one and a half million visitors and pumped more than $325m into the local economy.

On helping to revive the neighbourhood few would challenge the claim that the festival has had a positive impact.