The labor dispute over Tesla’s refusal to sign a collective wage agreement in Sweden has escalated into a dramatic labor battle.

Unions representing multiple industries announced this week that they would join the strike in solidarity with IF Metall, the Tesla mechanics’ trade union.

The standoff started in late October with a walkout led by IF Metall.

In Sweden, which doesn’t have minimum wage legislation for workers, about 90% of employees are covered by collective agreements involving unions and employers.

IF Metall describes the agreements as “the backbone of the Swedish model” and said it’s been trying to negotiate one with Tesla for the last five years.

The union said Tesla wages are below the industry average in Sweden, and it wants to secure better pensions and insurance guarantees.