OSLO, July 1 (Reuters) - Norwegian unions representing offshore drilling rig and floating platform workers entered state-mediated wage talks on Wednesday, aiming to avert a strike from Friday that could affect parts of the country's oil and gas sector.

The three unions, Styrke, Safe and DSO, have said more than 600 members could initially walk out, with the possibility of escalation. The wage agreement covers about 7,500 workers in total.

Any strike would initially affect Transocean's Encourage rig, Odfjell Technology's Linus rig, the AKOFS Seafarer well intervention vessel and Equinor's Gullfaks B platform.

It was not immediately clear how a strike would affect Norway's oil and gas output, which averages around 4 million barrels of oil equivalent per day (boepd).

The Gullfaks field in the North Sea produced about 22,900 boepd in 2025. Operator Equinor was not immediately available for comment.

A similar 10-day strike by workers on floating installations in 2018 led to the shutdown of Shell's Knarr field.

The unions reached a wage deal for workers employed directly by oil companies on June 5, averting disruption to production, but some workers employed by oil service firms went on strike on June 15.

The dispute has since escalated, with employers imposing a lockout affecting around 1,000 workers and warning of potential production impacts, and Safe expanding its strike by 63 workers from Wednesday.

Separately, oil firm Aker BP said on Wednesday it had to shut down the Tambar oil field in the North Sea because of the ongoing labour dispute. The field produced about 7,000 boepd in 2025, official data showed.

EnergiWatch first reported the shutdown.

Offshore Norway, representing oil service employers, has warned the oil service strike could cut Norway's oil and gas output by about 12,000 boepd this week, with losses potentially exceeding 120,000 boepd after mid-July if it goes on.

The government can intervene to halt a labour dispute if it threatens vital national interests, but so far the labour ministry has been reluctant to act.    

(Reporting by Nerijus Adomaitis, editing by Essi Lehto and Chizu Nomiyama)

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