Ratings agency Moody's has warned it may downgrade the credit rating of three French banks because of their exposure to Greek debt.
Credit Agricole, BNP Paribas and Societe Generale all face a possible downgrade because they could face losses on a Greek default.
Credit ratings are a measure of how likely a company or country is to repay its debts.
Moody's has already downgraded the credit ratings of eight Greek banks.
European leaders have yet to agree on the terms of a second bail-out for Greece.
On Wednesday, the country is expected to see another wave of general strikes against austerity measures.
In a statement, Moody's said: "Today's actions reflect Moody's concerns about these banks' exposures to the Greek economy."
Societe Generale and Credit Agricole both hold majority stakes in Greek banks.
BNP Paribas does not have a stake in a Greek bank, but Moody's estimates that it held about 5bn euros (£4.4bn, $7.2bn) of Greek government debt as of December 2010.