PHILADELPHIA (CNN) With United Auto Workers still patrolling the picket lines in their strike against General Motors, presidential candidates Bernie Sanders and Joe Biden spent Tuesday drawing sharp distinctions over their plans for health care in a way that could directly impact those on strike.

GM revealed that health care benefits for those on strike will soon come to an end, meaning the union will be forced to pick up the tab for COBRA coverage. Sanders, who has faced criticism over how his "Medicare for All" plan would impact unions and their negotiated benefits, argued that if his plan were the law of the land those striking wouldn't have to worry about their coverage.

"Here you have a situation with UAW is out on strike. 49,000 workers. I am sure that in that 49,000 there are family members who are seriously ill, and yet the greed of General Motors -- which has the amount of money to pay their CEO something like $21 million a year -- they cut off the health care benefits for those 49,000 workers," Sanders said.

"Under Medicare for All, every American -- whether you're working, whether you're not working, when you are going from one job to another job -- it's there with you."

Earlier in the day, at a presidential forum hosted by the AFL-CIO in Philadelphia, Biden took a subtle shot at the Sanders plan. Without mentioning Sanders or Medicare for All by name, the former vice president volunteered that his health care plan would protect the union's right to negotiate its own health care benefits with its employer.

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