The supervisors had planned protected strikes for part of their shifts on both days during their long-running pay dispute with the company.

Yesterday afternoon, BHP upped the ante by issuing a notice to the supervisors not to attend work for the balance of the shift when the action was to occur.

Illawarra Coal asset president Troy McDonald said the decision was not taken lightly.

"This is the only way the company can plan the ongoing activities of our operations with certainty," he said.

"Mining supervisors represent 6 per cent of the total workforce. The company has to minimise the disruption that this industrial action causes to other employees and contractors and above all has to ensure the safety of our people."

Association of Professional Engineers, Scientists and Managers of Australia (APESMA) chief executive Chris Walton said the lockout showed a lack of respect for the supervisors.

"Today BHP hit the panic button," he said.

"Mine supervisors want to work with BHP to fix this dispute by talking it through like adults."

Mr Walton said the notice from the company came through while the union was meeting with BHP to resolve the dispute.

The supervisors are calling for a pay increase they say would bring their salary packages into line with their peers at other mines.

Mr Walton said BHP's claims supervisors wanted an additional 27 per cent pay rise was not true.

BHP has said the pay claim is unrealistic and the supervisors' earnings are in the top 25 per cent of equivalent roles in the industry.