A potential strike at Stillwater Mining’s Nye Mine and its Columbus smelter in Montana got closer to happening as about 900 Stillwater Mining Co. union members rejected a new contract.

Members of the United Steelworkers Local 11-0001 rejected the contract extension, saying the offer did not include raises and kept healthcare and retirement benefits the same, The Billings Gazette reported. If the union does go on strike it will be the third time in 15 years that there has been a strike at the mine.

The labor official, who asked not to be identified because of the sensitivity of the talks, told The Gazette that the union and company would continue meeting about a possible contact extension. Union members are expected to go to work at least through midnight Friday, when their contract expires, the official said.

The four-year contract for the 900 workers had been scheduled to expire at the end of May but was extended for two weeks when the two sides reached a tentative agreement.

"We are disappointed that the tentative agreement was not ratified. Based on this decision by the union members, company management is considering all alternatives to create a situation that will best promote the long-term economic viability of operations at the Stillwater Mine and Columbus processing facility," Stillwater CEO Mick McMullen said in a written statement.

Miners told The Gazette that the new agreement would have changed their production incentives and resulted in less take-home pay.

Base pay for miners is about $30 an hour, not including incentives. Affected employees also include truck drivers, equipment operators and other support workers at the mine who work on different pay scales.

Negotiations grew testy when workers claimed they were being asked to take pay cuts as high as 25 percent while top company executives received raises this year.

Stillwater miners also walked off the job to strike in 2003 and 2007 for six and 10 days, respectively.

Billings-based Stillwater is Montana’s largest mining company and the nation’s only producer of platinum and palladium. The company operates mines at Nye and East Boulder in the Beartooth foothills and a processing and recycling facility in Columbus.

The labor negotiations were the company’s first under the leadership of McMullen, who started with Stillwater in 2013. He was hired after former Montana Gov. Brian Schweitzer led dissatisfied investors in a hostile takeover of the company.

A second contract covering workers at Stillwater's East Boulder mine south of Big Timber is scheduled to expire at the end of the year.