"Protests have been going on for six months, it's unprecedented," Sophie Binet, the new leader of the hardline CGT union said on BFM TV.
"There's a lot of anger but also fatigue," she said, adding that strikers were feeling the pinch on paychecks.
Between 400,000 and 600,000 people are expected to turn out at protests across France, authorities said, which would be down from more than a million who took part in marches at the height of the pension protests earlier this year.
But unions hope a big protest turnout could pressure lawmakers into reviewing the bill anyway and holding a vote.
Opposition lawmakers, meanwhile, say the bill being rejected would revive public anger, branding any such move "antidemocratic".
Persons:
Emmanuel Macron's, Sophie Binet, I'm, Jean, Claude Mailly, Macron, Michel Rose, Hugh Lawson
Organizations:
CGT, Inter, SNCF, Thomson
Locations:
Macron, France, Paris, Orly