House Republicans warned Tuesday that a proposal to add a repeal of Obamacare's individual mandate to tax reform legislation could make it harder to pass the bill in the House.

“I think we’d lose votes by putting it in,” Sen. Mike Simpson, R-Idaho, told the Washington Examiner.

House Republican leaders decided Tuesday they will not include a Senate proposal to add the mandate repeal to their own tax bill, which is scheduled for a vote Thursday.

But they have not ruled out adding it later to a final compromise bill agreed upon with the Senate GOP.

The provision would be added when the two chambers work on a compromise plan, Republican aides said.

The Senate is writing a bill in the Finance Committee and is expected to add the mandate repeal later Tuesday.

Senate Republican leaders said they have the 50 votes needed to pass their tax plan with the mandate repeal, which would add $338 billion in tax savings, according to the Congressional Budget Office.

But across the Capitol, House Republicans say many of their rank-and-file do not want to mix tax reform with a repeal of the Obamacare mandate because it does not include a provision to replace it. The mandate requires that people have health insurance or pay the government a penalty.

According to the CBO, stripping the mandate would cause premiums to jump by 10 percent each year because 13 million fewer people would sign up for health insurance coverage, particularly healthy people who would offset the costs of sicker enrollees.

Republicans said the the savings their constituents would get from tax reform would be lost to increases in health insurance premiums.

“It’s not the right thing to do,” Simpson said. “Because it doesn’t have a replacement. It’s a tough vote, no doubt about it.”

Many House Republican conservatives, however, have called for the mandate repeal to be included in the tax bill and praised the move by the Senate.

They called on the House to add the repeal to its version.

But centrists likely would balk, Republicans admit, and that could make it harder or even impossible to pass a final tax reform plan in the House.

House Republicans can afford to lose only 22 votes on the tax legislation. So far, a small faction of GOP lawmakers from high-tax states already have committed to vote against the bill because it eliminates the state and local tax deduction.

The mandate repeal would bring in more opposition, some lawmakers warned.

“There are a lot of our members who would like to do it, but there are some that don’t want to conflate healthcare and taxes,” Rep. Tom Cole, R-Okla., said. “I think the attitude here is let’s see what the Senate does. And it would obviously be an open topic in conference.”

The House Rules Committee is beginning work on the tax bill Tuesday and is not expected to add the mandate repeal.

That's a relief to most GOP lawmakers.

Rep. Adam Kinzinger, R-Ill., a member of the centrist Tuesday Group, made up of about three dozen members, is undecided on adding the mandate repeal to the tax bill.

“I am just hearing about this,” he said. “Our [bill] won’t have it, so we don’t have to deal with it yet.”