More workers in Norway's oil sector walked out of wage talks on Wednesday, sending the dispute to a state mediator and raising the prospect of a repeat of a 2012 strike.
Workers who operate onshore supply bases broke off talks, joining platform oil workers and oil service employees in breaking off wage negotiations, the Norwegian Oil and Gas Association, the energy companies' interest group, and trade union Industri Energi said.
"This was the third wage negotiation this year and the third one that is going to mediation," Jan Hodneland, the chief negotiator for oil firms said. "It is clear that the unions' expectation for this year's settlement is very different to that of employers."
The association said unions had made unreasonable pay demands for work on holidays and outside regular business hours.
Two years ago, some 10 percent of Norway's offshore workers went on strike for 16 days, cutting oil output by 13 percent and gas by 4 percent. The dispute ended when oil firms threatened a full lock out and the government stepped in to impose a deal.
The strike then pushed oil prices above $100 per barrel.
Supply base workers are vital to the sector because they provide offshore platforms with everything from drilling fluids to food.
The first of the mandatory mediations is scheduled for June 16-17 and unions said if talks fail, they would shut down two ExxonMobil and one GDF Suez platform with combined production around 80,000 barrels of oil per day.
Under Norwegian labour law, unions have to specify how many people and at what facilities would stop work in case of a strike. They usually provide such a list before mediation and start labour action immediately if negotiations break down.
Service and supply base workers have yet to provide such a list.
Some unions walked out of earlier talks on disagreements about wages and pensions but Indusri Energi, the biggest of the energy unions, cut a separate deal on both occasions.
This time however, Industri Energi also failed to reach a deal saying there needed to be more flexibility about working hours and pay.
(Reporting by Balazs Koranyi, editing by David Evans)