George Clooney has hosted a charity event for Italian VIPS and film industry insiders to raise money for victims of the crisis in Darfur.

Clooney, who is in Venice for Wednesday's premiere of the Coen brothers' film Burn After Reading at the 65th Venice Film Festival, swept past reporters as he arrived on Tuesday night for the fundraiser for his Not On Our Watch charity.

The event was expected to raise $US2 million ($A2.32 million), said Manuele Malenotti, the executive director of the Italian clothing company Belstaff, which sponsored the event.

Not On Our Watch has raised more than $US7 million ($A8.12 million) to help victims both of the humanitarian crisis in the Darfur region of Sudan and the cyclone in Burma, according to executive director Alex Wagner.

The charity, which was launched last year by Clooney, Brad Pitt and some of their Ocean's Thirteen colleagues, uses their celebrity appeal to bring attention to human rights abuses.

But it wasn't so easy to get even two of the founders together because of filming and family demands, Wagner conceded.

Pitt, who arrived in Venice earlier with his sons Maddox and Pax, was expected at the event, but hadn't arrived by the time cocktail hour was over. He also is appearing in the Coen brother's film.

"Scheduling is very difficult. Two of them happened to be in Venice at the same time because of the Burn After Reading premiere ... so there was a brainstorming session," Wagner said of the planned joint appearance.

Inside, Clooney was discussing the issues and where the charity puts its money at the fundraising dinner on Venice's Giudecca island, which will be attended by some 200 industry insiders and Italian VIPs, Wagner said.

One recent grant by the group was $US500,000 ($A578,000) in March to keep helicopters and aeroplanes flying aid into Darfur region of Sudan - topping off a $US1 million ($A1.16 million) donation a year earlier for the same program.

"We sent out a press release one day saying we were on the verge of closing it down and the next day we had $US500,000," said Bettina Luescher, a spokeswoman for the World Food Program at UN headquarters in New York City.

"They shine the light on the real emergencies and step up where we really need help."

Without that money, Luescher said the World Food Program had been on the verge of shutting down the air service to Darfur, which brings 3,000 aid workers a month to the stricken region. The UN food charity fed 3.3 million people there last month alone.

The air service is critical given deteriorating security, which makes road convoys vulnerable. Nearly 100 World Food Program food trucks have been hijacked this year alone.

Clooney has spoken for several years about the crisis in Darfur, where more than 200,000 people have been killed and about 2.5 million people displaced in three years of fighting between African rebels and government troops allied with Arab militia known as the janjaweed.

He went on a UN technical mission including Darfur and neighbouring Chad in January, sharing his impressions with reporters upon his return to draw attention to the crisis.