SAGINAW, Mich. — In strike votes at 21 Delphi Corp. plants across the country, members of the United Auto Workers union have overwhelmingly rejected the company’s plan to scrap its union contracts, fire three-quarters of its workers, cut the wages of the rest to “fast food” levels and kill retiree health care benefits.

Ninety-five percent of the ballots cast authorized the union’s leadership to call a strike, if needed, to defend the workers’ interests.

Delphi, which declared bankruptcy last year, manufactures auto parts. Its largest customer is General Motors. While Delphi has cried poverty, it recently sought court approval for a huge executive bonus program. The UAW represents about 24,000 workers at Delphi.

The International Union of Electronic Workers-Communications Workers of America, Delphi’s second-largest union with 8,000 workers, has already voted to authorize a strike if its contract is voided. In bankruptcy court hearings that began May 9, Delphi presented motions to reject its labor agreements and modify retiree benefits. Hearings are set to resume May 24.

UAW officials said they hope the strike vote will send a message to Delphi, and ultimately GM, that workers are willing to shut down production if necessary.

Saginaw is home to two Delphi plants. The company’s announcement that the plants may be put up for sale, downsized or closed has caused alarm. The city is already reeling from budget shortfalls, resulting in teacher layoffs and cuts in other vital services.

In the recent Cinco de Mayo parade, community groups including the Saginaw Area Democratic Club, Saginaw Progressive Forum, Democracy for America, Tri-City Action for Peace and One United Michigan joined with Delphi UAW Locals 467 and 699, Service Employees International Union 517M and Saginaw firefighters and police to march behind the banner “Saginaw Unite.”

A 10-point “Unity Charter for Jobs, Equality and Justice” brought the groups together. The charter includes demands for living wage jobs, universal health care, rebuilding neighborhoods, stopping the war in Iraq and bringing the troops home. It also calls for “fair trade,” forcing polluter Dow Chemical to pay for cleanup of the local rivers, and support for immigrant rights and affirmative action.

In an attempt to intimidate the union, Delphi has started to advertise for new workers in Saginaw and elsewhere. It wants to pay new hires between $10 and $14 an hour, even as it plans to cut thousands of hourly jobs nationally. Saginaw activists say the only way to win is to continue building unity between the community and workers at the plants.