London — Norway’s oil and gas output could be disrupted starting Friday as offshore workers are threatening strike action, employers’ group the Norwegian Shipowners’ Association said. Around 1,600 members of two trade unions, SAFE and Industri Energi, were set to strike if mandatory mediation talks on Thursday failed, the employers’ group said. The impact on production was unclear, but the Asgard C, Knarr and Statfjord C facilities are among those affected, as is the Johan Sverdrup development project. “Notice of collective work stoppage has been filed by SAFE for 667 members on 12 installations, and by Industri Energi 937 members on 20 installations,” the association said in an emailed comment. It said wage negotiations had broken down on May 28. Norway produced 1.6 million b/d of oil and 319 MMcf/d of gas in May, partly reflecting seasonal maintenance and, for gas, demand levels, as well as technical problems.