* 81 percent of workers who voted reject offer-union
* Strike nears one-month mark
* Caterpillar to take backup plan "to the next level"-spokesman
By Scott Malone
May 30 (Reuters) - Striking workers at a Caterpillar Inc plant in Joliet, Illinois, on Wednesday rejected the company's latest contract offer, an official with the International Association of Machinists and Aerospace Workers said.
Of roughly 800 workers at the plant, 620 voted, and 81 percent of them rejected the proposed contract. Union official Steve Jones said they did so because proposed pay raises were too small and it included higher health-care costs. The factory makes hydraulic components and other systems for Caterpillar loaders and mining trucks.
Jones said the workers plan to continue the strike they began on May 1.
The world's largest maker of earth-moving equipment is running the facility with management-level workers.
"Our sole focus now is on continuing to run the Joliet facility in a safe, efficient and productive manner," said Caterpillar spokesman Rusty Dunn. "With today's result, the company will now prepare to take the Joliet contingency work plan to the next level to ensure the facility's long-term success."
Talks between the union and the Peoria, Illinois-based company have broken off since the strike was called. Jones said the union offered to reopen negotiations after the vote but it was rebuffed by management.
"We told them we're available to meet when we notified them of the results, and they said if our position hasn't changed, there is no need," Jones said.
Caterpillar said there is "a significant gap" between the two sides.
"It is unfortunate that the union's unworkable and impractical approach to these labor negotiations has led to this result," Dunn said.
The strike follows a labor showdown last year between Caterpillar and workers represented by the Canadian Auto Workers union at a locomotive plant in London, Ontario. Those workers rejected a Caterpillar offer, and the company ended up closing the plant.