Train drivers at BHP Group Ltd.’s Pilbara iron ore operations in Western Australia have voted to strike on Friday morning for 24 hours, potentially cutting supply to the producer’s Australian export hubs.

Workers plan to carry out a stoppage under a campaign aimed at securing better working conditions and pay in an enterprise agreement, according to the Mining and Energy Union. The previous agreement, which covers about 580 drivers, shunters and trainees, was negotiated in 2014.

“Pilbara iron ore mine operators have had it their own way for a long time,” the union’s Secretary Greg Busson said in a statement. The workers had “been very patient and given BHP every opportunity to address their concerns,” he added. 

There are approximately 150 rail employees on-shift at any one time. Workers who strike will not be paid for those hours. 

BHP is “currently reviewing a revised set of claims provided by union representatives,” a company spokesperson told Bloomberg. “We believe that agreement can be reached without the need for protected action. We have contingency plans in place if action goes ahead.”

BHP shares closed 0.5% lower to A$46.07 in Sydney on Monday.

In Australia, industrial action is a legal right under the Fair Work Act 2009. It can be triggered when bargaining for a new enterprise agreement fails or an existing agreement is out-of-date, according to the Fair Work Commission.

A typical train iron ore train comprises of four locomotives pulling around 270 cars carrying 38,000 tons of iron ore, according to the company’s website.