NORMAL, Ill. (AP) _ The first United Auto Workers contract with Diamond-Star Motors provides a firm foundation for labor progress at the Chrysler-Mitsubishi joint venture, union officials said.

Many union members praised the three-year pact ratified Sunday, which provides wage and benefit increases of more than 30 percent.

The vote was 1,258 in favor to 383 against, said UAW spokesman Dennis Miller.

The $650 million Diamond-Star Motors plant began making cars about a year ago. The company, which employs about 2,900 people, produces sporty two-door sedans marketed as the Plymouth Laser and the Mitsubishi Eclipse.

Diamond-Star negotiators said Sunday they also were satisfied with the contract.

''I think it's fair for both the company and the workers,'' said Iven Boehm, a Diamond-Star spokesman.

Under the agreement, production workers who have been on the job 18 months get a base wage of $12.79 an hour, increasing to $17.01 an hour at the end of the three-year contract.

Maintenance workers, including skilled positions such as electricians and welders, begin at $14.89 an hour and increase to $19.49 at the end of three years.

The raises are intended to bring the wages of Diamond-Star workers into line with those of workers at other UAW-represented auto plants, and specifically with Chrysler plants.

The contract ncludes a ''me too'' provision that passes on to Diamond-Star workers any Chrysler increases that occur during the pact.

The job security provisions in the contract are ''among the strongest in the industry,'' according to a letter to members of UAW Local 2488 from Bill Stewart, regional director.

The company agreed not to lay off workers ''unless compelled to do so by severe economic conditions that threaten the long-term life of the company.''

Before laying off workers, the company would cut salaries of officers and management.