PARIS (AP) — France's national rail operator is recommending that passengers stay home Tuesday to avoid strikes over pension reforms that are expected to cause major transport woes but largely spare high-speed links to Britain, Belgium and the Netherlands.

Labour unions that mobilised massive street protests in an initial salvo of nationwide strikes earlier this month are hoping for similar success Tuesday to maintain pressure on government plans to raise France's retirement age.

Positions are hardening on both sides as lawmakers begin debating the planned change. France's prime minister, Elisabeth Borne, insisted this weekend that her government's intention to raise the retirement age from 62 to 64 is “no longer negotiable." Opponents in parliament and labour leaders are determined to prove her wrong.

Rail operator SNCF warned that major network disruptions were expected from Monday night to Wednesday morning, recommending that passengers cancel or postpone trips and work remotely if possible.

Rail services in the Paris region and regional trains across the country are expected to be severely affected, setting up a potential nightmare day for commuters.

Severe disruptions also are expected on France's flagship network of high-speed trains serving cities and major towns, including the Lyria service that links France and Switzerland, the SNCF said.

But it said high-speed Eurostar links with Britain and the Thalys services between France, Belgium and the Netherlands should run largely as normal.

Raising the pension age is one part of a broad bill that is the flagship measure of President Emmanuel Macron’s second term. The bill is meeting widespread popular resistance — more than 1 million people marched in protests against it earlier this month.

Macron stood firm on his plans on the eve of the strikes and protests.

“This reform is indispensable ... if we want to preserve and save the pension system,” he told reporters Monday after meeting with the Dutch prime minister.

Lawmaker Manuel Bompard, whose France Unbowed party is leading the parliamentary push against Macron's plans, called for “the biggest possible” turnout Tuesday in strikes and protests.

The government says its proposals are necessary to keep the pension system solvent as the life expectancy of the French has grown and birth rates have declined.

Unions and left-wing parties want big companies or wealthier households to pitch in more to balance the pension budget instead.

The bill went to a parliamentary commission Monday ahead of full debate in the National Assembly on February 6. Opponents have submitted 7,000 proposed amendments that will further complicate the bill's legislative passage.