The United States has an important role to play in helping guide Europe through its financial crisis, but it is ultimately Europe's problem to solve, the White House said Wednesday as President Barack Obama headed for an economic summit in France.

Obama left Wednesday evening on an overnight flight to France aboard Air Force One. The Group of 20 industrialized and developed nations meets Thursday and Friday in Cannes, a summit that's shadowed by the European debt crisis and Greece's surprise plans to put a bailout deal to a popular vote.

Press secretary Jay Carney said Greek Prime Minister George Papandreou's call for a referendum on the Europe bailout plan was certain to be a topic of discussion for Obama and world leaders.

Papandreou has infuriated European leaders and rocked financial markets, putting in jeopardy the long-sought deal to resolve the European debt crisis.

Without criticizing the Greek plan, Carney said it made clear the need for Europe to act.

"The events in Greece ... only underscore the need for Europe to come together and to unite behind conclusive action that resolves this crisis," Carney said at the White House.

He said that the U.S. has unique insight on the European financial crisis because of its experience dealing with its own financial crisis, as well as its position as the world's largest economy. But Carney made clear that the U.S. has no plans to offer financial support to Europe as cash-rich China may do.

"We have said that this is a European problem and that the Europeans have the capacity to resolve it, the resources necessary to resolve it, and need to take conclusive action to do so," Carney said.

"We have a role here to play because of our experience and knowledge, and of course, the fact that we are the largest economy in the world, and we can bring to bear insight and experience in a way that really no other nation can," he said.

The situation shows the limits of U.S. influence going into a summit where the focus may be on German Chancellor Angela Merkel and French President Nicolas Sarkozy and their work to resolve the crisis. Facing his own struggles with debt and deficits at home, Obama has few steps available to him overseas even though he acknowledges the threat to the struggling U.S. economy posed by the crisis in Europe.

Carney rejected the idea that that left Obama heading to the summit in France in a position of weakness, especially compared with China.

"Absolutely not," he said. "The United States is still the largest economy in the world. It is still the most powerful nation in terms of its alliances and its influence around the world. And that influence comes in a variety of ways, including the wealth of experience that we have."

"But the focus here is not on whether or not the Chinese involve themselves financially. I mean, that really is a sideshow to the focus here. The focus here is a European problem that requires a European solution."