French commuters endured a twelfth day of misery on Monday as the government and unions traded blame for a crippling transport strike over a pensions overhaul that has put holiday travel plans at risk for thousands.

Some 630 kilometers (390 miles) of traffic jams clogged Paris and its suburbs during the morning rush hour, nearly double the average levels, as most metro lines were again closed or operating just a handful of trains.

Across France, just one in three high-speed TGV trains and one in four regional trains were running, though most cities were not enduring the chaos seen in the capital.

Until now I�ve been working from home or taking my car, a man who gave his name as Francois told AFP at the Saint-Lazare station in Paris, saying he had left home at just before 5:00 a.m. But the car is no longer an option, because of the cost but also because it�s exhausting.

Unions plan a fresh day of mass demonstrations on Tuesday and insist the government must abandon planned pension reforms that they say could force millions of people to work longer before retiring.

Mass walkouts are again expected by teachers, hospital workers and other public employees as well as by lawyers protesting over plans to introduce a single pension system that would do away with 42 separate regimes.

The government has said it is willing to negotiate, in particular a pivot age of 64 that would grant rights to a full pension, but has defended a key project of President Emmanuel Macron�s wide-reaching reform drive.

Going on strike is legitimate, but you can also respect events like the year-end festivities, Environment Minister Elisabeth Borne told France 2 television, saying it would be irresponsible of union leaders to ruin vacations.

Rail operator SNCF has already warned that unless the strike ends in a few days, it will not have time to get service back to normal by December 25.

We�re going to try to make miracles happen for the Christmas holidays that begin on Saturday, SNCF�s Rachel Picard told the Parisien newspaper over the weekend.

If the government drops its project and we start serious talks on how to improve the system... everything will be fine, Philippe Martinez of the hardline CGT union said Sunday.

Otherwise, the strikers will decide on what to do on Thursday or Friday.