After weeks of student protests, France is set to be swept by broader, nationwide demonstrations Saturday over the cost of living, setting up a potentially fraught period ahead of presidential elections next year.
The prospect of the two movements merging, perhaps with outbreaks of violence, poses a big challenge to the government -- and an opportunity for far-left and far-right presidential candidates jockeying for power.
The country's Yellow Vest movement, which eight years ago staged street protests against President Emmanuel Macron and his government, called Saturday's "yellow and youth" demonstrations and urged millions to turn out.
It has appealed to teachers, workers, pensioners and farmers, as well as students, in an online call spread through social media.
"I have a feeling that (Saturday) will be a sort of culmination," 18-year-old Marie-Lou, a protesting university student in the city of Lille, told AFP.
"We'll be joined by workers and by the Yellow Vests, who are also mobilising again. There's a sense of hope that all these different struggles might converge."
Prime Minister Sebastien Lecornu on Friday ordered a crisis cell be set up to monitor the demonstrations in real time. On Thursday he said he feared clashes after what he called "urban violence" during the student protests.
Lecornu is under pressure to get a cost-cutting budget through parliament. It aims to tackle France's growing public debt by raising more tax revenue and reducing expenditures.
Yet the Yellow Vest and student movements are demanding the government spend more money.
They want protection from inflation, which has surged above three percent because of the Middle East war, and a boost to public services, particularly education.
There is also public anger at perceived police brutality during the student protests, during which several teenage protesters were maimed and thousands were arrested.
Francois Boulo, a figure within the Yellow Vest movement, told AFP the various groups expected to take part Saturday had not coordinated, "but we all had the same reaction when we saw the police violence against the students."
The growing unrest on France's streets and the country's fragmented political system are weighing on the final months of Macron's presidency, ahead of elections in April and May to choose his successor.
They are also fertile ground for opposition parties and their candidates.
Jean-Luc Melenchon, leader of the far-left France Unbowed party, has backed the student protests and marched in a demonstration Tuesday supporting them.
Far-right leader Marine Le Pen, the frontrunner according to surveys, has positioned her National Rally party on the side of the police, consistent with its law-and-order messaging.
Macron this week said he believed the "legitimate" demands of the protesting students were being "exploited for political purposes", according to a government spokeswoman.
Organisers of Saturday's demonstrations have set up a website showing more than 600 demonstrations planned across France, and hundreds more protest "actions" such as blocking motorway toll booths or service stations.
Both authorities and demonstrators were preparing for possible violence.
Paris's police banned a major march through the tourist and business heart of the capital, saying it could only take place in the east of the city.
They also launched legal action against a French influencer on Twitch who urged his hundreds of thousands of followers to take part in the demonstration "war zone".
And on Friday, Interior Minister Laurent Nunez told France 2 television that officers could use stun grenades in case of "extremely serious urban violence". He had previously suspended their use during the student protests after one stun grenade blew off the hand of a 15-year-old.
"Disturbances are expected, especially in the demonstrations in Paris and other big cities," an interior ministry official told AFP on condition of anonymity, citing a risk of violence from "the ultra-left movement".
"Actions blocking major roads or large, essential facilities will not be tolerated," the official said.
Demonstrators have set up their own smartphone app giving the real-time location of police, tear gas and helicopters.