France steeled itself for more clashes between demonstrators and riot police in Paris on Thursday after the government reversed course and authorised a union-led street protest against draft legislation to make hiring and firing easier.
With the police already stretched under a state of emergency imposed following Islamist militant attacks in November, more than 2,000 police will be deployed around the capital's Place de la Bastille square to control the march.
After violence and vandalism of properties on the fringes of protests in recent weeks, workers removed glass panes from bus stops and erected steel barriers along the route, while the Bastille underground station will be closed.
The protests against a bill that would loosen stringent laws protecting workers' rights pit President Francois Hollande's unpopular government against the hardline CGT which is fighting for its place as France's most powerful union.
In a months-long stand-off, neither side wants to cave in and lose face.
CGT leader Philippe Martinez accused Prime Minister Manuel Valls of pinning the blame for the escalating disorder on his group. He condemned the rioters but said the government had inflamed passions as unions sought a deal on the labour reforms.
"Every time we try to calm things down the prime minister throws fuel on the flames again."
Thursday's march begins at 14:00 p.m. (1200 GMT).
Protests in past weeks have been marred by hundreds of mostly masked youths engaging in running battles with police, hurling paving stones, smashing shopfronts and plastering anti-capitalist slogans on buildings. Police have said some CGT members were in involved in the violence.
The violent confrontations prompted the government to ban Thursday's march. It was the first time in more than five decades that a government banned a union march in a country where the right to protest is keenly guarded, in particular by the political left.
However, confronted by a backlash within its own traditional support base, the Socialist government backed down and allowed the march.
The unions want the government to shelve the bill that would make hiring and firing easier and devolve collective bargaining to company level.
The CGT and other allied unions argue that will lead to a fall in standards of labour protection. The government argues it is crucial to tackling a jobless rate stuck at 10 percent.
Opinion polls show two in three French voters are unhappy with the bill, which has already been watered down and is being debated by the Senate after Valls forced it through the lower house without a vote in the face of a ruling party rebellion.