President Emmanuel Macron's government wants to raise the retirement age two years to 64 and extend the period workers have to pay in as part of a reform it says is necessary to keep the system out of the red in the coming years.

Since his party lost its absolute majority last year, the government needs votes from the conservative Les Republicains to pass the unpopular reform in parliament.

While workers who started to work before age 20 would be allowed to continue to leave the workforce early under the reform, Borne said she was open to suggestions from conservatives that would benefit more workers.

"We are going to move by extending the measure for long careers to those who started working at 20 and 21. They will be able to retire at 63," Borne said in an interview with Le Journal du Dimanche Sunday newspaper.

A spokesman for the Republicains in the lower house, lawmaker Pierre-Henri Dumont, told Franceinfo radio the concession did not go far enough to win the party members' backing.

Borne said the move would affect up to 30,000 people and cost up to one billion euros ($A1.6 billion) per year, which meant a source of financing would need to be found.

Dumont said an alternative amendment proposed by his party would benefit "hundreds of thousands" of people per year.

Borne's government has faced two days of nationwide strikes since presenting the reform on January 10 with unions planning another on Tuesday.

Australian Associated Press