MELBOURNE Around 400 train drivers for BHP's Western Australian iron ore division will begin industrial action late this week after rejecting an offer on rostering that they say fell short, a union representative told Reuters on Monday.

Drivers will stop using a BHP app for roster changes, which means each worker must be contacted individually if the world's biggest miner wishes to change their working hours, Mining and Energy Union WA secretary Greg Busson told Reuters.

Drivers were trying to show some restraint by voting for action on the lower end of the scale to start, rather than disrupting operations straight away with stoppages where no one really wins, Busson added.

Workers had approved ballot plans late last month that could include strikes of 24 hours in the Pilbara region, which includes four processing hubs and five mines that are linked by more than 1,000 km (621 miles) of rail and port facilities.

The division accounted for $16.6 billion, or 60% of BHP's earnings before taxes last year. BHP did not immediately respond to a request for comment.

Drivers received an offer from BHP last Wednesday that did not meet their expectations around rostering arbitration and camp standards, Busson added. Most of Rio Tinto's trains are now driverless, so rosters are less of an issue.

BHP had asked its train drivers in 2021 to move to a two week on, one week off schedule as iron ore miners strived to ship out as much material as they could while prices were high and amid a squeeze on labour.

(Reporting by Melanie Burton. Editing by Gerry Doyle)