(Reuters) - The escalating euro zone crisis, with the threat of economic downturn and of increased contingent liabilities, could put France's AAA sovereign rating at risk, credit rating agency Fitch said on Wednesday.

In a special report on France's public finances, Fitch said the rise in government debt meant France's ability to absorb new shocks without undermining its triple-A rating had been largely exhausted.

Under a stress scenario whereby a further intensification of the euro zone crisis resulted in a much sharper economic downturn in France and across the region, and a material increase in the risk of contingent liabilities being crystallised, especially with respect to financial support for the banking sector, France's 'AAA' rating would be at risk, Fitch said in the report.

It also said additional fiscal measures were likely needed for France to reach its goal of a public deficit of 3 percent of gross domestic product in 2013, with Fitch seeing the 2013 deficit more likely around 4 percent.