Global miner BHP Billiton is facing a two-week work stoppage at its Illawarra Coal Appin Mine unit as some 50 supervisors demand for an 18 per cent increase in their pay. The workers strike is set to begin on Friday this week.

''This is a last resort for these supervisors,'' Catherine Bolger, Association of Professional Engineers, Scientists and Managers Australia collieries staff division director, said. ''They are incredibly frustrated at BHP's hardline antics."

They deserve to be paid fairly and in line with other mines in NSW and QLD," Ms Bolger said, noting the ballot result just proved the workers' level of dissatisfaction over their current pay rates.

But the strike is not seen as a potential game-changer as far as spot prices of coking coal is concerned.

"The end-user is not going to expect the same surge in spot prices when compared to the Queensland strike earlier on," Platts quoted an unidentified source, who noted "it's the supervisors who are going on strike, not the miners."

"At this stage, I don't think there is going to be a big effect, but if it goes on for a long time, then it might have an impact," the source said.

"These supervisors deserve to be paid properly. They are responsible for the safety of all mine workers, the handling of explosives and making sure mine production is smooth - their work delivers huge profits for BHP," Ms Bolger said.

''Industry pay rates for mine supervisors have increased over the last four years, yet Appin supervisors haven't received their fair share of that growth. They are now seeking an adjustment.''