The proposed Republican tax reform bill will include repeal of Obamacare's individual mandate requiring most Americans to have some form of health insurance or pay a tax penalty, GOP leaders said Tuesday.

The decision means that Republicans, yet again in 2017, will attempt to gut a key element of the Affordable Care Act.

So far, such efforts have failed because not enough Republican senators have backed the idea of repealing the mandate, which would lead to an estimated 13 million more people lacking health insurance.

"We're optimistic that inserting individual mandate repeal would be helpful," said Senate Majority Leader Mitch McConnell, R-Ky. on Tuesday afternoon after a lunch meeting with the Republican conference.

Sen. Tom Cotton, R-Ark., said, "I'm pleased the Senate Finance Committee has accepted my proposal to repeal the Obamacare individual mandate in the tax legislation."

"Repealing the mandate pays for more tax cuts for working families and protects them from being fined by the IRS for not being able to afford insurance that Obamacare made unaffordable in the first place," Cotton said. "I urge the House to include the mandate repeal in their tax legislation."

Senate Majority Whip John Cornyn, R-Tex., said, "We're going to repeal the tax on poor Americans."

Cornyn said the majority of people who pay the individual mandate tax penalty for not having insurance have lower incomes.

Sen. John Thune, R-SD, told the Washington Post that there are 50 Republican senators willing to support the mandate-repealing tax reform bill. That would be enough to pass it, with a tie-breaking vote from Vice President Mike Pence.

Thune also said the deal agreed upon is to pass that bill alongside another bill, known as Alexander-Murray, which would restore key federal subsidy reimbursements to Obamacare insurers cut off last month by President Donald Trump.