French arts workers on Friday extended a strike notice to the end of July, threatening a famed theatre festival in Avignon that draws tens of thousands of spectators.
The CGT-Spectacle union also called for a "massive strike" on July 4, the opening day of the Avignon festival, arguably the biggest event of its kind in the country.
Under French law, some 250,000 workers in the film, theatre, television and festival industry benefit from a system that compensates them for periods when they do not work, in a bid to address the job insecurity they face.
But many are unhappy with a deal reached between some unions, employers and the government in March to try to save money on this loss-making welfare regime. The agreement would increase their payroll taxes, among other changes.
They had issued a strike notice until June 30 and on Friday extended the notice to the end of July.
Prime Minister Manuel Valls said Thursday the state would foot the difference in the payments scheme until a final agreement was reached.
But the temporary concession failed to placate irate workers.
"If the government does not heed our demands with a fair and long-term plan that takes our proposals into account, the summer will not pass off normally!" a union statement warned.
The strike notice has already led to the cancellation of the Latin American Rio Loco festival in the southwestern city of Toulouse and hit events in Paris and elsewhere.
The last reform of this special welfare system in 2003 caused huge disruptions to the summer's festival season, forcing the cancellation of the Avignon event for the first time since its founding in 1947.