About 150 oil platform workers would go on strike, potentially disrupting output from several Norwegian fields, if they fail to get a pay deal by midnight on Friday, their union said on Tuesday.
Lederne, the smallest of the three Norwegian unions representing oil industry workers, said the strike would target platforms at Eni's Goliat, Shell's Draugen and Statoil's Kvitebjoern, Oseberg East and Gudrun fields.
"We believe it would mean shutting down production on those platforms," a spokesman for the union said.
The five fields together produced 326,000 barrels of saleable oil equivalent per day in March, according to Reuters calculations based on the latest figures available for individual fields from the Norwegian Petroleum Directorate.
A Statoil spokesman said he didn't want to speculate about the potential effect if the strike goes ahead. No one at Shell or Eni were immediately available to comment.
Lederne is an independent union, not affiliated with larger trade union organisations YS and LO, which reached a framework agreement with the employers' organization NHO earlier this year.
The two largest trade unions representing some 87% of all oil workers, Industri Energi and Safe, struck a deal with employers on 24 May.
The last strike of Norwegian oil workers in 2012 lasted for 16 days and cut the country's output by about 13% and its natural gas production by about 4%.