* Biggest union agrees to deal
* Two smaller unions hold out over pensions
* Talks go to mediator before any strike (Adds detail, union comments)
OSLO, May 9 (Reuters) - Wage and pension talks between Norwegian oil firms and two key unions broke down after three days of talks on Friday, raising the prospect of an offshore strike, but the biggest union cut a deal, the parties said.
The SAFE and Lederne unions, who represent over 3,500 oil workers held out, demanding better pensions, and their case will now go to a government mediator, a precursor to any strike.
“Pensions were not an issue we were willing to discuss,” said Jan Hodneland, the chief negotiator for Norwegian Oil and Gas Association, the employer’s interest group. “This was the case in 2012 as well, when they attempted to bring pensions into talks and we were hit with a strike.”
Two years ago, about 10 percent of Norway’s offshore workers went on strike for 16 days, cutting oil production by 13 percent, gas output by 4 percent. The strike pushed oil prices above $100 per barrel before the government intervened to end it.
SAFE said the main contention was pensions for just a few dozen workers. Unions wanted a lower retirement age for the workers, similar to others enjoyed by others in the sector, but oil firm were not willing to discuss.
Industri Energi, the largest oil worker union representing around 4,000 members, reached a deal, winning an average annual pay increase of 15,800 Norwegian crowns ($2,690)plus various supplements.
The date for the mediation has not been set. Although a breakdown in mediation could lead to a strike, the government may decide to impose a deal to avoid industrial action.
On May 13, oil firms begin wage talks with oil service workers. ($1 = 5.8830 Norwegian Krones) (Reporting by Gwladys Fouche; Writing by Balazs Koranyi, editing by William Hardy)