France's transport chaos deepened Monday on the fifth day of a nationwide strike over pension reforms, ramping up tensions at the start of a crucial week in President Emmanuel Macron's battle with trade unions.

With only two of the Paris metro's 16 lines running as normal and suburban trains also heavily disrupted, many commuters slipped behind the wheel to try to get to work in torrential rain, causing major gridlock.

Large queues formed at bus stops following an announcement that one out of two buses would be running but striking workers blocked seven out of 25 bus depots, leaving more travellers stranded.

With many having opted to work from home last week and only now returning to the workplace, this week will test public support for the strike.

A poll Sunday in the Journal du Dimanche newspaper showed 53 percent of the French supporting the strike or expressing sympathy for their demands, up six points in a week.

Unions have called a second day of mass protests for Tuesday, a day before the government unveils the full details of its plans for a single points-based pension scheme that does away with dozens of more advantageous plans enjoyed by train drivers, sailors, lawyers and other professions.

'A monstrosity'

Teachers are expected to walk out again for the second time in a week Tuesday, leading to widespread school closures.

Firefighters, electricity workers and "yellow vest" anti-government demonstrators have also joined railway workers in the streets in recent days.

The government's pensions envoy Jean-Paul Delevoye, who drafted the reforms, and Health Minister Agnes Buzyn will meet with trade unions on Monday to try to negotiate an end to the deadlock.

But the unions have sounded an uncompromising note.

"I will not negotiate over the implementation of what I describe as a monstrosity which endangers tomorrow's pensioners," said Yves Veyrier, the head of the militant Force Ouvriere union.

The strike has squeezed retailers in the run-up to Christmas, raising the prospect of another bleak year-end after the unrest caused by the yellow vests in late 2018.

The first day of the stoppage already caused an average 30 percent drop in sales, according to the Alliance of Commerce, which represents 27,000 supermarkets and clothing and shoe stores with almost 200,000 workers.

A hotel association said reservations in the larger Paris region dropped by 30 to 40 percent on the first day of the strike.

Regional and international trains, including the Eurostar to London and Thalys to Brussels, have also been hobbled by the unrest, and several flights were cancelled on the first days of the strike.

Fairer system for all?

Over 800,000 people took to the streets when the strike was launched on December 5, many accusing Macron of trying to weaken France's generous social safety net.

The president, Prime Minister Edouard Philippe and senior cabinet ministers met late Sunday to discuss the changes, which they argue will ensure a fairer and more sustainable system for all.

"If we do not carry out a far-reaching, serious and progressive reform today, someone else will do a really brutal one tomorrow," Philippe told Le Journal du Dimanche.

The strike has drawn comparisons with late 1995 when three weeks of strikes forced the then centre-right government to withdraw its pension reforms.

Adrien Quatennens, a lawmaker from the far-left France Unbowed party, acknowledged on LCI radio that the strike was hard on businesses and commuters, but said: "It's better to endure a few weeks of hassle than... years of hardship" in retirement.