Some 922 workers on Norwegian offshore oil drilling rigs and floating production platforms could potentially go on strike on June 28 unless a pay deal is agreed, Norway's largest oil workers union Industri Energi said on Wednesday.
The strike would hit oil companies' exploration efforts this summer. Past conflicts have also impacted some of Norway's oil production, such as last year's shutdown of Shell's Knarr field during a similar 10-day strike.
This year, a total of 15 floating installations, most of them at Equinor operated fields, such as Statfjord, Gina Krog and Johan Sverdrup, as well as at Knarr field, could be affected, the union said in a statement.
Equinor's spokeswoman said the company was aware of the potential strike, but declined to say whether it would have to shut production.
Shell was not immediately available to comment.
Companies drilling on behalf of oil firms in Norwegian waters include Transocean, Maersk Drilling Seadrill, Saipem and Odfjell Drilling.
Voluntary talks between the unions and the Norwegian Shipowners' Association broke down earlier this month, and a government-appointed mediator will attempt to broker an agreement by midnight on June 27.
If no deal is reached, the two unions are allowed to strike, and could potentially escalate the dispute over time.
Earlier, another oil workers' union, Safe, said it planned to take 667 workers on strike if the mediation failed. The union said on Wednesday it now planned to take on strike 673 workers.
Most members of the Safe union who could be taken out of strike are working on the same installations as those belonging to Industri Energi.
(Reporting by Nerijus Adomaitis, editing by Gwladys Fouche and David Evans)