PITTSBURGH, Pa. - It's a familiar pre-summit scene.

The metal barricades have been clamped down around Steel City and the police are on every street corner, in the air, and in the water. The protesters are taking crash courses on how to disrupt global talks without getting arrested, while the hotel staff bustle to make everything just so, for the throngs of international officials and media flooding in.

But the two-day G20 summit that starts today is not your run-of-the-mill leaders' meeting. The photo-ops and relatively empty rhetoric about global co-operation have been ditched at G20 meetings so far.

The Pittsburgh summit is just the third such meeting of this group of rich and emerging-market economies and the preceding G20 gatherings have made key decisions that mitigated the global recession and may well have set the stage for recovery.

The test for Pittsburgh is to see if the G20 can keep the ball rolling. Can the leaders agree to how to make sure the delicate recovery takes hold and doesn't disintegrate into another downturn? And can they adopt a framework that will prevent such financial crises from happening again?

"The G20, as a crisis committee, it looks good," said Andrew Cooper, associate director at the Centre for International Governance and Innovation, based in Waterloo, Ont.

"The question now is whether G20 declares victory or not," he said in an interview en route to Pittsburgh.

The first G20 summit led by former U.S. president George Bush in Washington during the last days of his tenure last November, and the follow-up summit in April in London, forged an unprecedented agreement among countries to buoy up their flailing banks. Leaders promised and delivered low interest rates and stimulus packages worth two per cent of their gross domestic products.

The co-operation helped restore global confidence that was eroding so quickly that it was compounding the problems caused by the global financial crisis, Cooper said. And the stimulus measures are now supporting a tenuous recovery in many countries.

Indeed, Toronto-Dominion Bank raised its forecast for global growth on Wednesday, saying the world economy will expand by 3.8 per cent next year - a full percentage point more than the bank's last forecast just three months ago.

But the TD forecast also predicts that the stimulus-fuelled growth in the last half of 2009 won't last into 2010. While the bank's economists don't predict a so-called "double-dip," the fear of a second bout of recession is hanging over the heads of the leaders as they meet in Pittsburgh.

"The world does have to be wary of a double dip," TD's chief economist, Don Drummond, said in an e-mail interview.