French President Nicolas Sarkozy on Tuesday said France is witnessing a "serious" economic and financial situation, after rating agency Standard & Poor's warned of mass downgrades of credit ratings of eurozone countries, including France and Germany, local media reported.

"The situation is serious. The country needs unity," Sarkozy said, noting that the agency's decision was made before Monday's Franco-German meeting.

Standard & Poor's on Monday said it might place on "negative" watch on ratings of 15 eurozone countries, and warned of possible downgrades in no later than three months if European leaders fail to forge an accord on ways to tackle the region's debt crisis during this week's summit in Brussels.

According to a brief statement issued by the Elysee Palace, Paris and Berlin has taken note of Standard & Poor's review decision, and "confirmed their determination to take all the necessary measures, in liaison with their partners and the European institutions to ensure the stability of the euro area."

Under heavy pressure to quell markets' fear, French President Sarkozy and German Chancellor Angela Merkel unveiled on Monday a common proposal for the European Union (EU) treaty changes aimed at imposing strict mechanisms of budget control and better governance in the region.