This follows the rating agency's downgrade of the outlook on the long-term sovereign credit ratings on the country to negative from stable, owing to what it called persistent economic and social problems.
The rating agency affirmed the banks' 'BBB+/A-2' ratings.
"The outlook revision on the sovereign reflects the potential for a downgrade if economic and social problems feed into the political debate in the run-up to the 2014 presidential elections and consequently further pressure the policy framework.
"The difficulty of addressing economic and social imbalances could be exacerbated by increasing external pressure in a context of sluggish global growth or investor risk aversion," the rating agency said.