STOCKHOLM, Nov 15 (Reuters) - Tesla (TSLA.O) is facing growing pressure in Sweden from unions backing mechanics demanding a collective bargaining agreement with the U.S. carmaker, with workers at one of its suppliers set to go on strike next week.

Tesla has no manufacturing plant in Sweden but its electric cars are serviced at workshops across the country, where around 130 mechanics affiliated with Swedish union IF Metall began a strike on Oct. 27.

They were soon joined by dockworkers and car dealerships who refused to handle Tesla products.

About 50 unionised workers at Hydro Extrusions, a subsidiary of Norwegian aluminium and energy company Hydro (NHY.OL), will stop work on Tesla car products next Friday, a spokesperson for the company said. The rest of the plant, located in the city of Vetlanda, will keep running, the spokesperson added.

Hydro Extrusions's Vetlanda plant makes aluminium profiles - aluminium alloys transformed into shapes, and is the first Tesla supplier in Sweden to down tools in support of the mechanics' strike.

Tesla did not immediately respond to a request for comment.

The carmaker told IF Metall on Nov. 6 it did not want to sign a collective agreement, the union said.

"We want Tesla Sweden to sign a collective agreement... We want this conflict to be as brief and short as possible," IF Metall spokesperson Jesper Pettersson said.

German unions have pressured the carmaker to implement a similar agreement for its 11,000 workers in Gruenheide, near Berlin.

It raised wages by 4% earlier this month, but German union IG Metall claims wages remain around 20% below those offered under collective agreement