French President Nicolas Sarkozy (R) welcomes German Chancellor Angela Merkel
Media playback is unsupported on your device
Video

G20 leaders gather in Cannes as Papandreou summoned for talks

The G20 leaders gathering in Cannes must wrestle with a world economy on the brink of real crisis.

Greece's surprise decision to put its European bailout to a referendum has shaken markets and infuriated Europe's leaders.

German Chancellor Angela Merkel warned the rescue package is "not up for renegotiation."

The Greek prime minister has been summoned for urgent talks.

From Cannes, Gavin Hewitt reports.