Union leaders themselves acknowledge it is a now-or-never moment before the draft law heads to parliament, where President Emmanuel Macron's party holds a majority and is widely expected to push through the overhaul by summer.
In Paris, protesters will march through the city from 11am to a square close to from the Elysee Palace, where ministers will meet to officially unveil the reform.
The route of Friday's march. Map: Google maps
“We're going to show that faced with this acceleration, this stubbornness by the government, ours is just as strong,” Yves Veyrier of the hard-line Force Ouvriere (FO) union told France Info radio on Thursday.
It will be the seventh day of mass rallies since a crippling transport strike was launched on December 5th by unions hoping to force Macron to back down on his push for a “universal” pension system.
The reform would sweep away 42 separate regimes, some dating back hundreds of years, that offer early retirement and other benefits to public-sector workers as well as lawyers, physiotherapists and even Paris Opera employees.
But critics say the new points-based system will effectively force millions of people to work longer.
Metro traffic in the capital was again disrupted on Friday, the 51st day of strikes, though services had almost returned to normal this week as unions shifted their focus to power cuts, port blockades and other protests.
Rail traffic was less affected, with most TGV and international trains operating as normal, and a majority of regional trains still running.
But the Eiffel Tower is again be shut for the day as some workers join the protests, the company operating the monument said.
Limited economic hit
Paris police are again bracing for potential violence after previous rallies were marred by vandalism and clashes with security forces, often by far-left “black bloc” protesters, leading to dozens of injuries and arrests.
But the government has faced accusations of condoning heavy-handed police tactics after a series of videos showing officers striking detained marchers or firing rubber bullets at point-blank range drew outrage on social media.
Yet despite a series of concessions, including a pledge to police, pilots and many transport workers that they will still be able to stop working before the official retirement age, the government has largely held firm with a reform promised by Macron during his 2017 presidential campaign.
He says the new system will be more transparent and fairer, in particular to women and low-income workers such as farmers.
Macron also appears determined to succeed where previous governments have failed when tackling France's sprawling pension system.
So far, the strike does not appear to have only mildly dented France's economy overall, though many businesses reported steep revenue declines over the crucial holiday shopping season, especially in Paris.
Analysts at IHS Markit reported on Friday that its index of French economic activity slowed in January from the month before, “signalling the slowest rate of expansion since last September”.
“While there were warnings of softer conditions in the service sector, linked to national railway strikes, manufacturing displayed mild signs of revival,” it said.
France's largest union, the moderate CFTD, has suspended its strike ahead of talks with the government on how to finance the pension overhaul, but other unions are insisting the plan be dropped completely.
On Friday, the FO and the CGT, the powerhouse unions in the public sector, called for a new day of walkouts for January 29th.