Passengers unable to travel because of the strike would be reimbursed the full cost of their tickets and a voucher for the same amount. AFP
Transport Minister Clement Beaune called the stoppage over the the coming weekend "incomprehensible and unjustifiable".
"It will probably cost the company around a 100 million euros," he told Franceinfo radio. "We don't need that at the moment and we need everyone to start talking again."
Several hundred thousand travellers have seen their tickets cancelled this weekend, the first Christmas since 2019 without major Covid-19 health concerns.
The SNCF has offered to reimburse double the face value of cancelled tickets if travellers are unable to book an alternative.
"I'm totally fed up. It's becoming a nightmare. You can't take people as hostages like this," pensioner Christian Petit told AFP at a station in Lyon.
Resolving the dispute, which has led to the cancellation of two out of five long-distance trains this weekend, is complicated by the way the strikers have organised themselves.
The stoppage has been coordinated by an informal collective of train managers on Facebook, rather than via union representatives, and the strikers have made no public statement.
The SNCF says unions have already negotiated a pay rise of 12 percent over two years for staff, which is in line with inflation and superior to most private-sector settlements.
"We've done everything to try to avoid the strike," SNCF boss Jean-Pierre Farandou said on Thursday.
More disruption looms over the New Year weekend when unions have informed management of another possible strike.
"What we expect from the management of the SNCF today is that they find a solution in the next few hours, and I mean in the next few hours," Economy Minister Bruno Le Maire told Sud Radio.