A few key Senate Republicans are already raising concerns with the discussion draft of a health care bill unveiled Thursday, which could threaten its passage if the measure comes up for a vote next week.

Multiple senators raised concerns with the draft they were briefed on Thursday morning, although many said they needed to review the proposal in full. Senate GOP leaders can only lose two Republican votes on the measure for it to pass with Vice President Mike Pence casting the tie-breaking vote as no Democrats are expected to vote for the measure. GOP leaders hope to bring the legislation to the floor for a vote next week.

“Conservatives have always been for repealing Obamacare,” Sen. Rand Paul told reporters Thursday. “My concern is this doesn’t repeal Obamacare.”

The Kentucky Republican said the continuation of several of the 2010 health care law’s regulations — a number of which the House wanted to allow states to waive — is a top concern. He also voiced concerns about the amount of money directed to help stabilize the individual insurance markets created under the 2010 law.

“Instead of trying to fix the death spiral of Obamacare, it simply subsidizes it with taxpayer money to insurance companies,” he said.

Paul released a statement later, along with Sens. Ted Cruz of Texas, Mike Lee of Utah and Ron Johnson of Wisconsin, which said the four Republicans could not, at this time, support the measure. 

“Currently, for a variety of reasons, we are not ready to vote for this bill, but we are open to negotiation and obtaining more information before it is brought to the floor. There are provisions in this draft that represent an improvement to our current healthcare system but it does not appear this draft as written will accomplish the most important promise that we made to Americans: to repeal Obamacare and lower their healthcare costs,” the senators said in their statement. 

On the other side of the GOP ideological spectrum, there were also worries about the measure. 

Maine Sen. Susan Collins, a moderate and a key swing vote, said in a statement she “has a number of concerns.”

Likewise, Nevada Sen. Dean Heller also said in a statement he has “serious concerns” about how the bill would affect Medicaid beneficiaries in his state.

“As I have consistently stated, if the bill is good for Nevada, I’ll vote for it and if it’s not — I won’t,” said Heller, who faces re-election next year.

Sen. Bob Corker of Tennessee told reporters the nonpartisan Congressional Budget Office’s estimate of costs and health care coverage effects would likely be released Monday.

The proposal is still subject to change, Sen. Lamar Alexander, chairman of the Health, Education, Labor and Pensions Committee, told reporters.

“There’s a virtually unlimited opportunity to amend this draft on the Senate floor,” the Tennessee Republican said of the reconciliation process the GOP is using to advance the health care measure. “I’m going to look at it in terms of the effect it has on Tennesseans.”

South Dakota Sen. John Thune, the GOP conference chairman, suggested the bill could be refined to secure enough votes for passage.

“There’s a lot areas that are subject to dials: tax credits, Medicaid, but I think right now, we’ve got members who are going to be interested in seeing it, digesting it and then looking to see if there are things we can do to refine it and make it more acceptable to more members to get to 50. I think the challenge is how to we get to 50,” he told reporters.

Others suggested they could support the measure.

Louisiana Sen. Bill Cassidy, who voiced opposition to the measure the House passed in May, told reporters that the Senate draft appeared to meet the “Jimmy Kimmel test,” referring to the late-night comedian’s tearful speech last month about his infant son’s hospitalization and the importance of ensuring that sick people could access care. But Cassidy warned he still needed to review the full proposal.

He also said the bill seemed to meet President Donald Trump’s test of being less “mean” than the House bill, as the president reportedly told a group of GOP senators.

“The issue is, if your loved one gets sick, would they have adequate coverage? As best I can tell, it does, but I again need to read the text,” the Louisiana Republican said.