On Thursday, the protest will gather workers from the public sector but also those from the private sector such as lawyers.
The RATP, Paris' public transport system which includes buses, trams and metros, will be heavily impacted, as 11 out of 16 metro lines will be completely closed, while only a third of buses will be available.
French President Macron wants to set up a single points-based pension system in which each day worked earns points for a worker's future pension benefits.
Currently pension benefits are based on a worker’s 25 highest earning years in the private sector and the last six months in the public sector.
Public sector unions fret their workers will come out worse because under the current system the state makes up for the chronic shortfall between contributions and payouts in the sector.
Unions also worry they will lose their say on contributions and benefits under a centrally managed points-based system.
Unions have criticized Macron for turning a deaf ear to him as he lost little time early in his presidency pushing through a labor law reform and easing taxes for investors. They are also furious that he ignored their input for a much delayed unemployment insurance reform presented in June.
Polls show the French are deeply attached to keeping the official retirement age at 62, which is among the lowest in OECD countries. Public workers who do arduous or dangerous jobs, such as mariners, can leave years earlier.
Critics also say that delaying the retirement age would punish those who start their careers in their mid 20s after long studies.
LFI leader Jean-Luc Melenchon called for a massive mobilization tomorrow, to reject a reform with which 'everyone is going to lose.'
Regarding the promise of guaranteeing pensions above 1,000 euros with the single points system, which would replace the 42 current regimes, the leader told public television that "the problem is those who do not have the total number of years of contributions, this is the case of women and those in precarious employment."
Melenchon warned that a similar system has already affected retired persons in Sweden, and even more so women.
The LFI leader urged authorities to avoid repression and guarantee peace during the protests, after the government announced the mobilization of thousands of security officers to supervize the protests.