Tram and metro workers in Helsinki are threatening a two-day strike next week unless the city reconsiders a plan to incorporate the city transport authority HKL.
Tram and Metro Staff Union president Petri Lillqvist called the plan to turn the municipal authority into a limited company in January "an extreme measure".
The new firm would at first be owned by the cities of Helsinki and Vantaa.
The Tram and Metro Staff Union says that unless the city commissions a new study of the proposal, it will launch a shutdown on Thursday and Friday, 16-17 September.
"We really hope that the city employer understands the seriousness of the matter for the employees and all residents of Helsinki. The last thing we want to do is to cause inconvenience to our passengers. But this is a cry for distress on behalf the traditional HKL, which is something that we all share," said.
Last Tuesday, tram and metro maintenance staff staged a 24-hour walkout to protest the incorporation plan.
The Helsinki City Council was to have considered the plan at its meeting last Monday, but left it on the table.
Last summer, more than half of HKL's 1200 employees signed a petition questioning the incorporation plan. Many have expressed concern about a slide toward full privatisation, which they say would lead to weaker working contracts, quality and safety.