(CNN) Hillary Clinton said Tuesday that Congress should repeal the unpopular "Cadillac tax," an Obamacare tariff on premium health care plans.

Her position is a win for unions, who vehemently opposed the tax, set to go into effect in 2018.

Clinton said that while the Affordable Care Act -- one of President Barack Obama's top legislative achievements -- was "working, plain and simple," there were some changes that needed to be made.

"I have proposed new reforms to build on the progress we've made and lower out-of-pocket costs for families," said Clinton in a statement. "That's why, among other steps, I encourage Congress to repeal the so-called Cadillac tax, which applies to some employer-based health plans, and to fully pay for the cost of repeal."

Clinton said some of her proposed reforms to Obamacare, which she has rolled out in the past month, would more than cover the cost of repealing the Cadillac tax, a measure that helped to pay for the health care reform law.

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