Citing safety risks, the SNCF national rail network warned travelers to stay home or use "alternative means of locomotion" to get to work Monday instead of thronging platforms in hopes of getting the few available trains.

As a result, the national road authority reported more than 600 kilometers (360 miles) of traffic problems at rush hour around the Paris region — up from 150 kilometers (90 miles) on an average day.

The road traffic was worse Monday than when the strike started last week, because many French employees managed to work from home or take a day off then. But that's increasingly difficult as the strike wears on.

Fortified by the biggest nationwide demonstrations in years when the strike launched last Thursday, unions plan new protests Tuesday, and hope to keep up the pressure on the government to back down on the retirement reform.

Only about a sixth of French trains were running Monday, and only two of Paris' 16 subway lines were functioning normally. International lines also saw disruptions, and union activists blocked bus depots around Paris, limiting bus routes, too.

French President Emmanuel Macron summoned Prime Minister Edouard Philippe and other top officials Sunday night to strategize for a crucial week.

The prime minister will present details of the government's plan on Wednesday. It's not expected to change the official retirement age of 62 — but it is expected to encourage people to work longer.

The reform is central to Macron's vision for transforming the French economy. Government ministers insist the current system is unfair and financially unsustainable, while unions say the reform attacks fundamental worker rights and will force people to work longer for less.