Industrial action at BHP's Port Hedland operations in Western Australia began on Saturday, marking the first major strike there in more than two decades.
BHP ships some $80 million of iron ore daily through Port Hedland, the world's biggest iron ore export hub. It has previously said it has plans to ensure that operations can continue.
About 150 workers are expected to take part in the strike on Saturday, the Combined BHP Ports Unions (CBPU) said, which is only a portion of BHP's workforce at the port of more than 800 people.
A CBPU spokesperson earlier said that the nature of the industrial action, a 24-hour ship-loading ban followed by a 24-hour stoppage, remained unchanged.
The CBPU is negotiating a four-year bargaining agreement with the world's third-largest iron ore miner, and opted to go ahead with the industrial action despite progress in talks between the parties on August 4.
About eight ships are expected to finish loading from BHP ports over the weekend, a source familiar with the matter said.
The action is not expected to affect rival miners Fortescue (FMG.AX) and Hancock Prospecting, which also use Port Hedland. The hub accounted for 75% of total iron ore exports from the Pilbara region of Western Australia in the year to June.
BHP has been negotiating for more than seven months with the CBPU, which represents around 450 operators and maintenance workers, over a new pay deal amid record share prices and rising costs of living. The CBPU will next meet with BHP on August 18, the same day that it will report its annual results.
