Norway’s Fellesforbundet said it would block the transit of Tesla cars into Sweden if the US automaker refuses to sign a Swedish collective wage agreement by December 20th.

Since October 27th, some 130 mechanics at 10 Tesla repair shops in seven Swedish cities have been striking to protest against the carmaker’s refusal to sign a collective agreement.

The strike has since grown into a larger conflict between Tesla and almost a dozen unions seeking to protect Sweden’s labour model.

Despite this, several Swedish media have reported that the impact of the strikes has so far been fairly limited.

IF Metall has accused the electric carmaker of systematically using strike breakers to circumvent the labour action, and some Tesla deliveries to Sweden have been redirected through neighbouring Norwegian and Danish ports instead.

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 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.

“If this is not in place by December 20th, we will go ahead and take action,” Norway’s Fellesforbundet union said, without disclosing what kind of measures it was planning.

“This is a clear message to Tesla that it will not be able to redirect Swedish Teslas to Norway,” he added.

Danish union 3F earlier this week said its transport workers would launch a strike in solidarity with Swedish Tesla workers on December 18th unless a solution was found.

According to the Swedish Transport Agency, there are 51,617 Teslas registered in Sweden.

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