Denmark’s biggest union 3F said on Tuesday its transport workers would launch a strike in solidarity with Tesla workers in neighbouring Sweden on December 18th if Tesla refuses to sign a Swedish collective wage agreement.

“All members of 3F Transport are covered by the solidarity movement. This means that dockers and hauliers will not unload Tesla cars nor transport them into Sweden,” 3F said in a statement.

The Swedish strike, launched by the metal workers’ union IF Metall, began on October 27th when some 130 mechanics at 10 Tesla repair shops in seven cities walked off the job.

It has since grown into a larger conflict between the US electric car giant and almost a dozen unions seeking to protect Sweden’s labour model.

“Solidarity is the cornerstone of the union movement and stretches beyond national borders,” the chairman of Denmark’s 3F Transport, Jan Villadsen, said in Tuesday’s statement.

“Even if you’re one of the richest companies in the world, you can’t impose your own rules. We have labour market agreements in the Nordic region, and you have to respect them if you want to run a business here,” he said.

Negotiated sector by sector, collective agreements with unions are the basis of the Nordic labour market model, covering almost 90 percent of all employees in Sweden and 80 percent in Denmark, and guaranteeing wages and working conditions.

Despite the fact that many of Tesla’s employees in Sweden are union members, they cannot benefit from the collective bargaining agreements unless Tesla signs on to them.

Tesla chief executive Elon Musk has long rejected calls to allow the company’s 127,000 employees worldwide to unionise.

Marie Nilsson, the head of IF Metall, told AFP the conflict was “a clash between the Swedish or the European culture and the American way of doing business”.