The United Auto Workers on Tuesday warned Detroit's Big Three car makers not to expect any help from the union when it comes to shouldering the burden of mushrooming US health care costs, Reuters reported.

The warning, against any attempt to "shift" medical costs onto workers, came from UAW president Ron Gettelfinger, who spoke in a rare news conference ahead of next month's opening of what promises to be tough talks over a new collective labour agreement, the news agency said.

"Make no mistake about this, we are not going to shift health care in negotiations with the Big Three," Gettelfinger reportedly said. "We are not going to pick up premiums, we are not going to pick up co-pays, we are not going to pick up deductibles."

General Motors, Ford and Chrysler have said repeatedly that health care costs – and their obligation to provide virtually free medical care for UAW workers – put them at a huge disadvantage with foreign automakers, Reuters noted.

"Of all the issues we face, health care is probably the most intractable," Ford chairman and chief executive Bill Ford Jr. told the company's annual shareholders meeting on Monday, the report said.

Reuters said Ford spent $US2.8 billion on health care last year alone, more than company officials say it spent on steel for its cars and trucks, and GM, the world's largest vehicle maker and largest private purchaser of health care in the United States, spent $4.5 billion.

But Gettelfinger, reiterating comments he made when he laid out the UAW's bargaining position for the first time in March, said the problem of health care was bigger than the US motor industry and something that could not be resolved in labour talks with the UAW, Reuters said.

"It's a national problem, it demands a national solution," Gettelfinger reportedly said.

Reuters noted that the UAW's last pact with Detroit's car makers, described by analysts as the richest in US labour history, was signed in 1999 at a time when the Big Three were all enjoying a profit windfall. The situation has changed dramatically since then, however, as the companies struggle under high fixed-costs, excess production capacity, a punishing discount war and relentless assault on the US market from abroad, the news agency added.

Apart from health care, critical issues in Detroit's upcoming labour talks include plans to close plants -- something prohibited under the current agreement -- and the UAW's expected demands for job security and higher wages, Reuters said.

On pensions and employee retirement plans, another big issue for GM, Ford and Chrysler, Gettelfinger signalled he would oppose any major changes there too, Reuters said.

The news agency said the UAW chief dismissed the drug-benefit plan being considered by Congress as something that "falls short of the mark" and said drug companies spend more on advertising than they do on research. "I think that national health care is the only solution," he reportedly said.