The U.S. Commerce Department said it was investigating recent steel price hikes to determine whether some market participants were "illegitimately profiteering" from 25 percent tariffs introduced by Trump on steel imports.
New spending by some of the world's largest iron ore miners is tightening the market for jobs and support services in Australia's biggest mining region.
Privately held Dundas Mining is restarting its Avebury nickel mine in Tasmania early next year and Swiss trading house Transamine has secured the offtake.
The union had earlier asked the company to negotiate by 10:00 a.m. local time but said in a statement later on Monday that it had begun preparing for a strike.
