Some conservative groups pan GOP's Obamacare repeal and replacement plan Hard-line Republicans spoke out against the measure soon after its introduction.

 -- A number of conservative groups and lawmakers on Capitol Hill have lined up today against the newly-unveiled GOP plan to repeal and replace Obamacare, saying the Trump administration-backed proposal falls short of their vision for a Republican Obamacare replacement.

House GOP leaders released their much-anticipated proposal Monday evening, ahead of committee markups on Wednesday. They hope to pass the measure -- which eliminates Obamacare’s individual mandate and offers a series of tax credits in place of subsidies to help people buy insurance -- through the House by the end of the month.

Hard-line Republicans spoke out against the measure soon after its introduction, taking issue with its proposed refundable tax credits and the 30 percent penalty for coverage lapses.

“The problems with this bill are not just what’s in it, but also what’s missing: namely, the critical free-market solution of selling health insurance across state lines,” Club for Growth President David McIntosh said in a statement.

“Rather than accept the flawed premises of Obamacare, congressional Republicans should fully repeal the failed law and begin a genuine effort to deliver on longstanding campaign promises that create a free market health care system that empowers patients and doctors,” Heritage Action Chief Executive Officer Mike Needham said.

FreedomWorks, another conservative group, is planning a day of protests against the new proposal later this month.

On Capitol Hill, a number of conservative senators and members of the House Freedom Caucus have also criticized elements of the proposal. Republicans can afford only two defections in the Senate in order to pass the measure if it comes to a party-line vote -- which is expected given Democrats' opposition to the proposals.

“I believe when you look through it, it is Obamacare in a different form,” Rep. Jim Jordan, R-Ohio, said in a news conference Tuesday.

Sen. Mike Lee, R-Utah, said that the bill is a “step in wrong direction.”

“It's a missed opportunity,” Lee said.

House Energy and Commerce Committee Chairman Greg Walden, R-Oregon, urged critics during a news conference today to “actually read the bill."

When House Ways and Means Committee Chairman Kevin Brady, R-Texas, was asked about criticism of the proposal as "Obamacare Lite" and not a real conservative replacement, Brady said, “This is Obamacare gone.”

In a statement today on behalf of the White House, Health and Human Services Secretary Tom Price endorsed the legislation.

“Your legislative proposals are consistent with the President’s commitment to repeal and replace the Affordable Care Act,” Price said in a letter to Walden and Brady released today.

Speaking to reporters at the White House today, Price called the bill a "work in progress" when asked if the White House supports the details of the measure. "This is an important process to be had," he said of the debate and criticism of the bill on Capitol Hill.

Conservatives suggested Tuesday that they would be open to negotiating, and supporting the measure if the tax credits and other portions were amended.

“Conservatives want a seat at the table and we want to repeal Obamacare,” Sen. Rand Paul, R-Kentucky, said at the news conference.

Trump met with the House GOP whip team at the White House today to discuss the proposal, as Vice President Mike Pence spoke with senators and leaders of the conservative House Freedom Caucus on Capitol Hill.

"This will be a plan where you can choose your doctor, this is a plan where you can choose your plan, and you know what the plan is, this is the plan,” Trump said. “It's a complicated process but actually it's very simple -- it’s called good health care."

Trump said the measure has "tremendous" support despite some of the GOP backlash.

Rep. Tom Cole, R-Oklahoma, who attended the whip meeting, said Trump made it "abundantly clear" that he "intends to work very hard" to persuade members currently against the bill to vote for the proposal.

"He's good at closing a deal," Cole said.

House GOP Chief Deputy Whip Patrick McHenry, R-North Carolina, said Trump is keeping track of members who are opposing the GOP plan.

"The president is paying attention to what people are saying and doing, what they’re saying and where they’re doing it, he is highly aware and has a highly-attuned ear to what is happening in the press," he told reports on Capitol Hill after the meeting.

Minutes later, Trump tweeted at Sen. Paul.

In a brief news conference Tuesday afternoon, House Speaker Paul Ryan, R-Wisconsin, said Republicans will have 218 votes to pass the measure when it comes to the House floor later this month.

Republicans unveiled the bill Monday night without a "score" from the Congressional Budget Office, a nonpartisan cost-estimate that would also project any coverage changes.

Walden told reporters that lawmakers will have and release the CBO score before the full House votes on the measure. An aide to House Minority Leader Nancy Pelosi said the score would not be available until Monday, March 13th.

ABC's John Parkinson contributed to this report.