Governments have previously given into street protests
Hundreds of thousands of protesters took to the streets of Paris on Sunday in a demonstration designed to ratchet up the pressure on the government ahead of a key meeting on controversial pension reform.
The unions leading the march said some one million people had taken part, brought into the capital from around France on special trains and buses, although police put the turnout at 300,000.
The protest is part of an ongoing campaign of industrial action against the right-wing government's pension reform plan, which would make employees contribute for longer to claim a full pension.
The bill is to be put to cabinet for approval on Wednesday. If it is not amended to take account of the protests, unions have threatened to launch a further wave of crippling strikes.
French Prime Minister Jean-Pierre Raffarin says his plans to make employees pay more over a longer period towards their pensions are urgently required in order to shore up a growing deficit.
The shortfall, which has mounted as the "baby boomers" generation goes into retirement, is expected to reach 50bn euros (£36bn; $57.4bn) by 2020.
The unions agree that the disproportionate ratio of workers to pensioners is a problem, but insist there are other ways of finding the money - notably by asking companies to share more of the burden.
Pension reform has always proved controversial in France - the last right-wing government was forced to retreat from attempts to overhaul the system after crippling transport strikes in 1995. It then lost an election two years later.
Mr Raffarin insists he will not allow the protesters to intimidate his government away from reform.
But our correspondent says there is little reason for expecting the government to have enough sticking power to impose its view, particularly in the face of opinion polls backing the protesters' cause.
It does however have an overwhelming majority in parliament and the backing of President Jacques Chirac, who remains a popular figure.
A first strike is expected to kick in on Tuesday, with air traffic controllers planning a day of industrial action.
Air France said on Sunday it would be forced to cancel more than 60% of its short and medium-haul flights on account of the strike.