March 12 (Reuters) - The U.S. United SteelWorkers (USW) union members voted on Thursday to overwhelmingly reject what energy giant BP called its "last, best, and final" contract proposal to those working at its Whiting refinery in Indiana.

The USW stated in a release that "an unprecedented 94% of union members voted Thursday and 98.3% voted not to accept BP's offer."

BP had presented the union with a Last, Best and Final offer (LBFO) last week, and said that the offer would expire in 10 calendar days.

USW has said that after two months of negotiations, BP's proposal came with changes to the basic terms of the contract including limiting the union's ability to strike and stripping its bargaining rights, base wage cuts across classifications, elimination and outsourcing of 100 union jobs, ending seniority protections in case of layoffs, and more.

United Steelworkers Local 7-1, which represents around 800 workers at the largest refinery in the U.S. Midwest, said its bargaining committee has reported the results to BP and will give the company an opportunity to present a more serious proposal.

BP in a response late Thursday confirmed that its represented workforce at its Whiting refinery has voted not to ratify the company's "final" offer.

"BP will continue to bargain in the best interests of our employees, our company, and the community," the company added.

Eric Schultz, president of USW 7-1, said the company has recently tried to divide the union, with management even offering members donuts during their shifts, while they have also threatened the loss of health insurance and being locked out.

Since their contract expired on January 31, the union has been working under rolling 24-hour extensions of their previous agreement.