As the Tribeca Film Festival kicks off today, the five-year-old event — created in the wake of 9/11 to rejuvenate Lower Manhattan — seems ratcheted up several notches amid the gala debut of Universal’s lightning-rod pic “United 93” tonight and a PR blitz that will draw Tom Cruise as well as Gothamites’ rapt attention.

Fest founders Robert De Niro, Jane Rosenthal and Craig Hatkoff were joined Monday by their programming guru, Peter Scarlet, and a few boldface names (Josh Lucas, Edward Burns) at an opening press conference where De Niro was revealed, again, to be the in-demand face of the fest if not its public voice.

Rosenthal did most of the talking, though the press corps’ queries were virtually all lobbed De Niro’s way during a Q&A.

“We continue our mission without being defined by it,” explained Rosenthal of the fest’s persona as both a sprawling haven for unknown auteurs as well as studio tentpoles, from “Mission: Impossible III” to “Poseidon” and “Over the Hedge.” “Part of the festival is having fun and having a party, and stars do that.”

Even as so many regional fests cast about for an identity, Tribeca has found its relevance during its brief existence. It took in 4,100 submissions this year compared to 1,300 when it first kicked off. Fest also has expanded outside the neighborhood for which it is named: In partnership with AMC, screenings are being held all over Manhattan.

At Monday’s press conference, held at the Tribeca Performing Arts Center, De Niro drew the largest response from shutterbugs. Whenever the thesp paused to look up from his prepared remarks, the loud crescendo of cameras clicking drew a round of laughs from the audience and even the actor.

But as in past years, De Niro seemed downright uncomfortable in the spotlight; making his prepared comments, he came last in a line that included Rosenthal, Lucas, Burns, director John Polson, American Express exec John Hayes and the Empire State Development Corp.’s Charles Gargano.

Lucas is one of the fest’s jurors this year, joining Mark Cuban, Laurence Fishburne, Moby, Ken Burns and Whoopi Goldberg, all announced Monday.

“It’s great to see how the festival has continued to grow,” De Niro said, “and how it’s impacted the neighborhood.”

But perhaps reflecting Tribeca’s growth in relevance five years on — as developers, politicos and civilians argue over Ground Zero’s development and Hollywood networks and studios begin to roll out 9/11-themed pics, the questions De Niro faced were not softballs.

When asked if he is disappointed that there hasn’t been any major building begun at the site of the Twin Towers, the actor hemmed and hawed before blurting out, “It’ll get done.”

He then made a dash away from the podium and let Gargano weigh in on the thornier issues. (Gargano pointed out how important De Niro’s investment has been in rebuilding the area.)

“I’m not that good at articulating,” De Niro admitted when asked whether it was the right time for pics like “United 93” to be unveiled. “See it! When I saw it, I agreed.” He looked over and smiled at his partner and sheepishly added, “Ask Jane.”

But the icon’s shyness was perceived as endearing as he stumbled for words or mugged for the camera. In a world of so many soundbites, the show was unusual but refreshing.

Of aud readiness for “United” and other such pics, Rosenthal said, “9/11 was the most photographed even in the world. Artists have digested it, and it is an important time. We deal with it every day.”

She said repeatedly that “United” — which has been a focus of controversy before its opening — is one of many similarly themed pics screening here, though most of the rest are documentaries.

She pointed to “The Saint of 9/11,” “The Heart of Steel” and “The War Tapes” as highlights.

Though Tribeca has been a marketing marvel, Rosenthal still wants the fest to become more of a hotbed for business; she pointed to the acquisition of “Transamerica” last year by the Weinstein Co. as evidence that the fest was making strides in that direction.

Event has yet to become a feeding frenzy like Sundance or Toronto, where bidding wars lead to deals sealed on the spot. Pacts at Tribeca usually dribble out after the confab winds down or are announced during the fest for PR purposes after being done weeks earlier.

But producers who have been regulars in Sundance and Toronto are saying they see Tribeca as more of an option now.

“We put a lot of thought into Tribeca,” said Tribeca-based producer Robert May, whose SenArt Films has the Iraq docu “War Tapes” in the festival and whose credits include fest faves “The Station Agent” and “The Fog of War.” “We’ve never had a project there, and it seemed like this year Tribeca was ready.” May also recently wrapped “Bonneville,” starring Jessica Lange, Kathy Bates and Joan Allen.

It does seem as if more acquisitions players are paying attention. Whereas junior execs might have been dispatched in the past to keep an eye on pics, this year seems to be bringing in more execs from Los Angeles.

It remains to be seen whether the fest can deliver after a boffo opening.