Denmark’s largest trade union has joined strike action by Swedish Tesla workers, piling pressure on the US electric car company to agree to collective bargaining rights for its employees. Members of the Swedish trade union IF Metall have been on strike for six weeks – attracting support across industries, including from postal workers, painters, electricians and dock workers who have all launched secondary action. So far, Elon Musk, Tesla’s chief executive, appears to have been far from sympathetic – first decrying secondary action at PostNord as “insane” and then mounting legal action against the Swedish transport agency and the postal service over the failure to deliver licence plates for new cars. The Danish union 3F Transport, responding to a request from IF Metall, is joining the action in a “sympathy strike” aimed at preventing dock workers and drivers from receiving and transporting Tesla cars going to Sweden. All members of the union are covered by the sympathy strike. The announcement comes amid speculation that Tesla could attempt to circumvent Swedish dock worker strikes by delivering their cars to Danish ports and transporting them by truck to Sweden. Jan Villadsen, the chair of 3F Transport, said he hoped the move would help bring Tesla to the negotiating table. “IF Metall and the Swedish workers are fighting an incredibly important battle right now. When they ask for our support, we are of course behind them. Just like companies, the trade union movement is global in the fight to protect workers.” he said. “With the sympathy strike, we are now stepping in to put further pressure on Tesla. Of course, we hope that they come to the negotiating table as soon as possible and sign a collective agreement.” In what appeared to be direct criticism of Musk, Villadsen added: “Even if you are one of the richest in the world, you can’t just make your own rules. We have some labour market agreements in the Nordic region, and you have to comply with them if you want to run a business here.” IF Metall’s contract secretary, Veli-Pekka Säikkälä, welcomed the news, saying: “We are happy that Danish trade unions are closing up.” He declined to comment on whether other Nordic countries were also planning sympathy measures. Fellesforbundet, the largest union in the Norwegian private sector, has previously said it would be prepared to block Swedish Teslas from coming to the country.