WASHINGTON: Republican White House hopeful Mitt Romney has appeared to contradict previous campaign statements by saying President Barack Obama's health reform law entails a “tax” and not a penalty.

Romney, who enacted a similar healthcare overhaul when he was governor of Massachusetts, has had to reassure fellow conservatives who despise so-called “Obamacare” without appearing to flip-flop on his own legacy.

The balancing act was evident in an interview with CBS news on Wednesday in which Romney agreed with the Supreme Court's ruling that the individual mandate—which requires Americans to purchase health insurance or pay a fee—amounts to a tax and not a penalty, as both he and Obama had previously argued.

“The Supreme Court has the final word. And their final word is that Obamacare is a tax. So it's a tax,” Romney told CBS Wednesday.

“They decided it was constitutional. So it is a tax and it's constitutional,” he said, adding that he had agreed with the court's dissent, which said the mandate was unconstitutional.

That appeared to mark a shift in his position, given that Romney campaign aide Eric Fehrnstrom had told MSNBC on Monday that the Republican candidate had “consistently described the mandate as a penalty.”

Republicans were enraged by the Supreme Court's narrow vote last Thursday to uphold the health care law, but generally agreed with the part of the decision that called the individual mandate a tax.

They have since accused Obama of raising taxes on the middle class and made the allegation a central plank of their campaign to deny him a second term, arguing that the health law further burdens an already weak economy.

However, for Romney to accuse Obama of raising taxes through the health care reform would open the Republican candidate—long dogged by charges of flip-flopping—to similar charges of raising taxes in Massachusetts.

Romney attempted to finesse the issue in the CBS interview by insisting that states have the right to enforce such mandates.

“And as a result, Massachusetts' mandate was a mandate, was a penalty, was described that way by the legislature and by me. And so it stays as it was.” Romney has vowed to repeal “Obamacare”—officially known as the Affordable Care Act—on his first day in office, but has defended his own law, saying individual states have the right to reform their own health care systems.

The Obama campaign was quick to accuse Romney of contradicting himself, saying in a statement: “Romney has called the individual mandate he implemented in Massachusetts a tax many times before.