Doubt cast on France's triple-A credit rating by Moody's raised uncertainty over Europe's hopes of drawing a line under its sovereign debt crisis, five days before a crucial EU summit.
The U.S. ratings agency said late on Monday it may slap a negative outlook on France's Aaa rating in the next three months if slower growth and the costs for helping bail out banks and other euro zone members stretch its budget too much.
"The deterioration in debt metrics and the potential for further contingent liabilities to emerge are exerting pressure on the stable outlook of the government's Aaa debt rating," Moody's said in its annual report on France.
The warning, which sent the risk premium on French government bonds shooting up to a euro lifetime high, came as European Union leaders are preparing measures to protect the region's financial system from a potential Greek debt default.
That strategy includes new steps to reduce Greece's debt, strengthening the capital of banks with exposure to troubled euro zone sovereigns and leveraging the euro zone's rescue fund to prevent market contagion to bigger economies.
The October 23 summit is likely to agree to leverage the bailout fund by allowing it to guarantee a portion of newly issued euro zone debt, euro zone officials said.
With about 300 billion euros of its 440 billion-euro capacity still available, by guaranteeing the first 20-30 percent of any losses, the European Financial Stability Facility could stretch three to five times further.
"This idea is the main contender," one official said.
Economy Minister Francois Baroin insisted that France's AAA status was not at risk but acknowledged that the 1.75 percent growth forecast on which the government has based its 2012 budget was over-optimistic and would have to be revised down.
"The triple-A is not in danger because we will be even ahead of schedule on passing deficit reduction measures," Baroin said on France 2 television.
"We will do everything to avoid being downgraded."
Asked if next year's growth outlook would have to be reduced in light of weak economic prospects, he added: "It is probably too high compared to the development of the economic situation.
France and Germany, the two strongest economies among the 17 euro zone members, form the backbone of the EFSF rescue fund and are drafting a crisis-fighting strategy for Sunday's summit.
Without France's triple-A rating, the whole edifice of rescue measures for troubled peripheral euro zone states would begin to crumble, putting more weight on Germany, where there is a strong public backlash against bailouts.
German leaders on Monday doused market hopes of a miracle cure at Sunday's Brussels summit, saying no one should expect a "definitive solution.
Analysts said the ratings agency's move was unusual, since it had not put France on ratings watch, but it was a signal to the government that it needed to adopt a more realistic growth assumption and adjust its budget measures accordingly.
Monday's review was only a preliminary step, but a negative outlook would be a sign that Moody's could downgrade its rating on France in the next couple of years. It placed the United States's Aaa rating on negative outlook in August.
The two other major ratings agencies, Standard & Poor's and Fitch, reaffirmed Paris' triple-A rating in August when French banks came under fierce market pressure over their exposure to the weakest euro zone sovereigns.
FRENCH SPREAD HITS RECORD
The spread on French 10-year bonds over benchmark German bonds jumped to a 16-year high of 101 basis points, more than 1 percentage point and safe-haven German Bund futures rose on ebbing hopes of a quick solution to the debt crisis.
European shares fell, partly due to news that China's growth slowed slightly more than expected in the third quarter. chief Josef Ackermann, who is also chairman of the IIF, resisting pressure on both fronts.
Ackermann has objected to efforts to force banks to raise more capital and IIF lead negotiator Charles Dallara told Reuters on Monday that bigger writedowns on Greek bonds could only happen if policymakers addressed broader sovereign debt issues in Europe.