French President Nicolas Sarkozy warned Thursday that Europe was facing an unprecedented risk from its debt woes and said a crucial EU summit was the last chance to solve the crisis. "Never has Europe been so necessary and never has it been in so much danger... Never has the risk of Europe's explosion been so great," Sarkozy said in a speech in Marseille ahead of the summit's start later Thursday. "We must act straight away. The longer we wait to take this decision, the more it will cost and the less effective it will be," he told a meeting of European conservative parties. "If we don't have an agreement on Friday, we will not have a second chance," Sarkozy said. He also said Europeans had only "several weeks" to act to save the eurozone, which is facing a sovereign debt credit crisis that has raised fears of a collapse of the single currency union. France and Germany were working Thursday to drum up support for their plan to save the eurozone, which would amend EU treaties to include legal or constitutional limits on deficits and automatic penalties for eurozone nations that overspend.