Global credit rating agency Standard and Poor's (S&P) has warned that it could downgrade the credit rating of most euro zone nations.

In a statement issued Monday, the rating agency said it placed 15 euro zone members on watch for a possible downgrade. The two members of the economic block that were not put on credit watch were Cyprus, which currently is under review, and Greece, which already holds the worst rating in the world.

Generally, countries that are put on the S&P’s negative credit watch have a 50 percent chance of seeing their credit rating downgraded within 90 days.

The rating agency said “systemic stresses” in the region have grown in recent weeks to the degree that they now put downward pressure on the credit standing of the whole euro zone.

The agency’s announcement came as leaders of France and Germany sought a new accord that seeks to penalize euro zone countries whose budget deficits run too high.