Moody's Investors Service on Wednesday placed France's top three banks, BNP Paribas, Societe Generale and Credit Agricole (CASA), on review for a possible downgrade, citing the banks exposure to Greece's debt crisis.
"Today's actions reflect Moody's concerns about these banks' exposures to the Greek economy, either through direct holdings of government bonds or credit extended to the Greek private sector directly or through subsidiaries operating in Greece, a key factor for CASA and SocGen due to their local Greek banks," Moody's said in a note.
Euro zone ministers failed on Tuesday to reach agreement on how private holders of Greek debt should share the costs of a new bailout, putting the onus on the leaders of Germany and France to forge a deal later this week.
The ratings review helped weigh on the euro, already under pressure after a Financial Times report saying a German-inspired Greek debt rescheduling plan could force euro-zone governments to provide up to an extra 20 billion euros ($29.2 billion).
Greece became the lowest-rated country in the world on the scale used by Standard & Poor's, which downgraded it this week to eight notches below junk status.
Moody's said potential mitigants to its concerns were the banks' strong financial profiles, substantial scale and earnings diversification.
CASA's and BNPP's reviews were unlikely to lead to downgrades of more than one notch, while SocGen's debt and deposit ratings could be downgraded by as much as two rating notches, it added.
"Moody's may take similar actions on other banks with direct exposures to Greece in the coming weeks, if it considers that their ratings may be inconsistent with the potential impact of a Greek default or restructuring," the ratings agency said.
"Additionally, we are closely monitoring the risks that would likely result from a Greek default scenario, e.g. the potential impact on weaker countries, the capital markets, and funding conditions, and are taking those risks into consideration in our ratings of banks across the euro zone."
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