British Prime Minister David Cameron on Saturday reminded G20 leaders they must do everything in their power to remove obstacles to world growth and avoid slipping back into protectionism. G20 nations, which represent 85 percent of the global economy, meet in France on November 3 and 4 and have pledged to come up with concrete steps to boost growth as the world economy skids. Cameron, in Perth for a Commonwealth leaders summit, held talks with his Australian counterpart Julia Gillard Saturday and said both of them agreed on the urgency in tackling imbalances in the world economy. "On the G20 agenda, we both agree we've got to remove the obstacles to world growth, whether that is a deal in the eurozone, whether it is making sure there is no slide back into protection, whether it's dealing with the imbalances," he told reporters. International Monetary Fund chief Christine Lagarde warned this month the weakness of advanced economies was "beginning to hit emerging countries" that had supported the world economy during the previous economic crisis. The Commonwealth bloc includes five G20 members -- Britain, Australia, Canada, India and South Africa.