French President Emmanuel Macron's much-disputed plan to raise the retirement age by two years to 64 moved forward on Wednesday as a select group of lawmakers from both houses of parliament agreed a compromise text, despite nationwide protests.

But approval of the deeply unpopular bill - which has faced huge street protests and repeated job walkouts - by the lower house of parliament on Thursday is far from a done deal.

Ruling party officials have acknowledged the numbers there were tight and lawmakers from the conservative Les Republicains (LR) and centrist groups said they were being courted by ministers hoping to convince them to vote the changes through.

It should not be too hard to get the Senate's approval, as it is dominated by LR.

If too tight for comfort in the lower house, the government may resort to a procedure known as “49:3”, which would allow it to push the text through without a vote. That would ensure the text was adopted but would risk anger on the streets.

Opinion polls show a vast majority of voters oppose the changes, and unions, and protesters, have warned they will continue their mobilisation even if the bill is voted through on Thursday.

"We will continue the fight no matter what,” said Philippe Martinez, the head of the hardline CGT union.

"If they vote for this reform, I don't think things will go down well, because we see that blue-collar workers, communities of workers have gone against this reform. People have had enough,” Yvonnick Dauve, a welder and unionist in Ancenis-Saint-Gereon, said at a march in western France.

Disruptions to train services and air traffic will continue on Thursday, as will a garbage collectors' strike that has seen more than 6,000 tonnes of rubbish pile up in Paris. France's energy sector has also been hit hard.

Macron and his government say the changes to the pension system, one of the most generous among industrialised nations, are necessary to keep the pension budget in the black. At stake for the president are not just financial gains, however, but also his reformist credentials.

One key question will be the cost of the measures agreed by Macron's camp to get LR's support, including a softener for those who started to work early, and a top-up for working mothers.

The government had initially said that pushing back the retirement age by two years and extending the pay-in period would yield an additional 17.7 billion euros in annual pension contributions, allowing the system to break even by 2027.

There was no official estimate on Wednesday of the impact of the compromise deal.

But Philippe Vigier, a centrist lawmaker who was part of the select group that negotiated the deal, told reporters that tweaks to the initial draft bill cost billions, and accounts would now be balanced in 2030.