DETROIT – In the end, the first nationwide strike against General Motors Corp. in 37 years came because the United Auto Workers want something that GM will find difficult to promise: Job security.

UAW officials said the 73,000 UAW members who work at about 80 U.S. facilities for the nation’s largest automaker didn’t strike Monday over what many thought would trip up the talks: A plan to shift the retiree health care burden from the company to the union. They said they also didn’t strike over wages.

They said union members walked out because they want GM to promise that future cars and trucks such as the replacement for the Chevrolet Cobalt small car or the still-on-the-drawing board Chevrolet Volt plug-in electric car will be built at U.S. plants, preserving union jobs.

The strike puts GM, which is restructuring so it can better compete with Asian automakers, in a bind as some of its new products begin to catch on with consumers. But it also means workers are taking a big risk – giving up pay and slowing down GM in an uncertain economy.

“Job security is one of our primary concerns,” UAW President Ron Gettelfinger told reporters Monday afternoon after talks broke off and the strike began. “We’re talking about investment and we’re talking about job creation” and preserving benefits, he said.

Talks resumed a short time later as sign-carrying picketers marched outside plant gates.

Worker Anita Ahrens burst into tears as hundreds of employees streamed out of a GM plant in Janesville, Wis., just after the strike began at 11 a.m. EDT.

“Oh my God, here they come,” said Ahrens, 39. “This is unreal.”

Ahrens has seven years at the plant, where she works nights installing speakers in sport utility vehicles. She waited Monday for her husband, Ron Ahrens, who has worked there for 21 years.

The couple has three children, including a college freshman, and Ahrens worried about how they would pay their bills.

“This is horrible, but we’re die-hard union, so we have to,” Ahrens said. “We got a mortgage, two car payments and tons of freaking bills.”

The striking workers will receive $200 a week plus medical benefits from the UAW’s strike fund. The union had more than $800 million in that fund as of last November, according to the UAW’s Web site.

The UAW, Gettelfinger said, is willing to talk about taking money from the company to form a trust that would be responsible for billions of dollars in retiree health care costs.

GM wants the trust, called a Voluntary Employees Beneficiary Association, or VEBA, so it can move much of its $51 billion in unfunded retiree health care liabilities off the books, potentially raising the stock price.