The credit rating agency Standard & Poors warned Monday that Greece could be considered in default on its debts under a French proposal for private banks to agree to “roll over” loans to the Greek government.

The French proposal was designed to help Greece avoid defaulting on its private debt, but S&P said under its rating criteria, extending the loans “would likely amount to a default” because the banks would not make as much money as originally promised.

Governments and international institutions that are trying to help Greece avoid default on its debts have insisted that private investors and banks share the financial burden of supporting the government in Athens.

A group of private French banks that are major lenders to the Greek government proposed voluntarily renewing some of the bonds with different terms to avoid non-payment.