A major French union has warned Paris that the upcoming Euro 2016 soccer tournament opening could be disrupted unless it backs down on contested labor law reforms. It comes as tens of thousands of people hit the streets again to protest the legislation.

The warning on Thursday by the hardline CGT union took aim at the 2016 UEFA European Championship (known as Euro 2016), scheduled to begin in France on June 10. The match will be played at various stadiums throughout the country, including Bordeaux, Lyon, Marseille, Nice, and Paris.

But if the CGT has its way, those games will only be taking place if Paris agrees to back down on a highly contested labor law reform.

When asked by Reuters if his union was willing to disrupt the football contest, CGT chief Philippe Martinez said: “The government has the time to say 'let's stop the clock' and everything will be ok.”

Those thoughts were echoed by the head of the smaller FO union, Jean-Claude Mailly, who said: “In football speak, it's time the prime minister took the red card back.”

The unions' statements came as tens of thousands of people hit the streets in protest on Thursday, leading to clashes between police and demonstrators, Reuters reported.

Around 100 people targeted a police station in the southwest city of Bordeaux, throwing objects at it and damaging a patrol car. Bank windows were broken in Paris and the western city of Nantes, prompting police to respond with tear gas.

Protesters also aimed to choke off power and fuel supplies and paralyze the public transport network on Thursday, with employees halting their work at oil refineries, nuclear power plants, and railways. Demonstrators also erected road blocks and burned wooden pallets and tires at major ports and near key distribution hubs.

The street rallies were also joined by marchers from the youth protest movement Nuit Debout (Up All Night).

But despite employee walk-outs, street demonstrations, and threats from unions, French Prime Minister Manuel Valls has rejected calls to scrap the part of the labor reform law which has most angered the CGT. That section would allow companies to opt out of national obligations on labor protection if they adopt in-house deals on pay and conditions with the consent of the majority of employees.

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"There is no question of changing tack, even if adjustments are always possible," said Valls.

The prime minister also stated that the government would break up refinery blockades. His statements were supported by the country's other large union, the CFDT.

The Thursday protests are the latest in a string of demonstrations in recent weeks, in which 350 police officers and several protesters have been injured and more than 1,300 people arrested.

Protests against the labor law reforms have been taking place since they were put forward by Labor Minister Myrian El Khomri. The government says the reforms – which focus on fighting unemployment by loosening protections on France's 35-hour work week and layoffs, and reducing overtime bonuses – will help curb the country's high unemployment rate. Protesters and workers' unions, however, say the government wants to make it easier and less costly for employers to lay off workers.

France's unemployment rate hit a record high in March, pushing jobless numbers to 3.591 million people, according to the Labor Ministry.