Maintenance workers went on strike on Wednesday at Woodside Energy's North West Shelf and Pluto LNG export plants in Australia after failed negotiations with contractor UGL.
Offshore Alliance, a grouping of the Australian Workers Union and the Maritime Union of Australia, said workers were taking action after UGL offered an enterprise agreement that was below industry standards.
"The end result of UGL's inability to negotiate or accept industrial standards is protected industrial action," the union said in a post on social media on Wednesday. The action would continue until an enterprise agreement was finalised, it added.
The Karratha gas plant is the onshore processing facility for the North West Shelf, Australia's oldest and second-largest LNG project, producing 14.3 million tonnes a year of liquefied natural gas.
The nearby Pluto LNG facility produces 4.9 million tonnes of LNG a year.
Woodside said it would continue to work with UGL management, but it was ultimately up to them to resolve the disagreement with their workers.
"We're talking about workers from UGL, and UGL work in a number of locations, some of which are supporting our business," CEO Liz Westcott said at an industry conference in Adelaide.
"We've been making sure we understand how to accommodate this. Working closely with our workforce has always been our priority, and we continue to have those strong relationships, so you know it's sort of part of life."
Offshore Alliance alleged in earlier social media posts the contractor was using third-party workers in an effort to drive down wages. The union group has organised prior strike votes at Woodside's Pluto 2 facility against contractor Bechtel.
It comes as unionised workers at Inpex's Ichthys LNG plant in northern Australia also served notice to strike from May 27, a move that could disrupt operations and exacerbate a global supply crunch caused by the conflict in the Middle East.
(Reporting by Helen Clark in Adelaide and Christine Chen in Sydney; Editing by Lincoln Feast.)
