RACINE, WI—UAW members who have been on strike since May at CNH Industrial factories in Wisconsin and Iowa voted down a tentative labor contract on Jan. 7, the United Auto Workers union said.

The union did not disclose how many workers at the two plants rejected the four-year deal, which included wage increases of 25 to 38 percent, according to CNH. Still, union members said the proposed contract failed to provide enough of a raise to combat inflation, additional vacation days or better healthcare coverage.

The UAW represents about 1,000 workers at the plants, and union officials had warned a rejection of the latest offer was likely.

“We’re going to notify the company and see if they are willing to come back to the table,” said Yasin Mahdi, the UAW local president in Racine, where the company employs about 700 people. “I hope the next time they come with a real, bona fide offer.”

CNH officials said the latest offer was its “last, best and final,” and in a statement encouraged employees to “reconsider their position in another vote.” The company said it will wait for the union to take the next step.

Workers in May had rejected an offer by the maker of agriculture and construction equipment that included an 18.5 percent wage increase over three years.

CNH brought in replacement workers to keep the factories operating once the strike began, union officials said. The plant in Racine, 60 miles north of Chicago, makes tractors and combines, while the Burlington, IA, facility builds loaders, backhoes and forklifts.