Half of the additional 1.5 billion euros will be provided by banks, an official at the ministry said.
French municipal borrowers have seen the cost of billions of euros in Swiss franc-linked debt spiral dangerously higher, forcing the state to lend them a helping hand.
Up until the 2008-09 financial crisis, many municipalities and local governments took out long-term loans linked to foreign currencies, offering low interest rates in the initial years and floating rates afterwards.