France is set to face widespread rail disruptions in early May after unions representing staff of national railway called for a new series of strikes.

The CGT-Cheminots, Société nationale des chemins de fer français (SNCF) largest union, has announced an indefinite strike beginning May 5, while Sud-Rail, which represents a significant number of train conductors, has called for walkouts on May 7, 9, 10, and 11, French broadcaster BFMTV reported on Thursday.

The action coincides with the long weekend around the May 8 national holiday, traditionally one of the busiest periods for travel across the country. The unions are demanding wage increases and improved working conditions for railway staff.

Transport Minister Patrice Vergriete warned that each day of strike action leads to €10 million (USD $10.7 million) in lost investments in the national rail infrastructure.

“Those who say they care about the rail network and public investment must also take responsibility,” Vergriete said. “By constantly calling for strikes, they weaken the very system they claim to defend,” he added.

Vergriete said he hoped the unions would “return to reason”, urging all parties to pursue social dialogue in good faith. “Negotiation can only take place if everyone is around the table and shows a willingness to de-escalate,” he said. “I don’t want to intervene directly because I think that would weaken the state.”