With a vote on the bill possible as soon as Thursday, members of the House Freedom Caucus, a conservative Republican faction, said they had been negotiating alterations to the plan with the White House.

Much of the discussion hinged on conservatives’ desire to scrap what are labeled “essential health benefits”—services that insurance plans are required to cover under the Affordable Care Act, commonly called Obamacare, such as mental health help.

“I can tell you that we’re making great progress,” Mark Meadows, chairman of the hardline conservative House Freedom Caucus, told reporters. “We’re not there yet. But we’re hopeful.”

Trump was to meet at the White House with members of the Freedom Caucus on Thursday at 11:30 a.m., the White House said.

But while the president courted conservatives, the bill appeared to be losing traction among Republican moderates, some of whom attended a meeting late Wednesday in House Speaker Paul Ryan’s office. Representative Charlie Dent, a leader of the “Tuesday Group” of House Republican moderates, issued a statement saying he could not back the bill.

“I believe this bill, in its current form, will lead to the loss of coverage and make insurance unaffordable for too many Americans, particularly for low- to moderate-income and older individuals,” Dent said in the statement.

The chairman of the House Rules Committee, which met all day Wednesday to set the rules for the bill’s consideration on the House floor, said late on Wednesday that the panel would resume its meeting on Thursday, having made no definite decision on the timing of the floor vote.

Repealing and replacing Democratic former President Barack Obama’s 2010 Affordable Care Act is a first major test of Trump’s legislative ability and whether he can keep his big promises to business.

Plans aired by Trump during his election campaign and his first two months in office lifted U.S. stock markets to new highs. But stocks fell back sharply on Tuesday as investors worried that a rough ride for the healthcare legislation could affect his ability to deliver on other big pieces of his agenda, from cutting taxes and regulation to boosting infrastructure.

Major stock indexes wobbled on Wednesday, with the Dow Jones Industrial Average ending slightly down and the S&P 500 slightly higher. Investors are eagerly awaiting Thursday’s healthcare vote, which could be pivotal for Trump’s broader plans.

The Freedom Caucus has objected to the bill because its members believe it is still too close to Obamacare.

Representative Steve King, a conservative who was among lawmakers who met Trump on Wednesday morning at the White House, said he would now vote for the bill because he got a commitment from Trump to publicly advocate a change to the legislation when it reaches the Senate, eliminating the essential benefits, which also include emergency room visits and maternity and newborn care.

“I have a full and firm commitment with many witnesses from President Trump,” King said in a video statement on YouTube.

Meadows said the members of the Freedom Caucus had also discussed the essential benefits with the administration. Conservatives say reducing or scrapping the mandates would bring down insurance premiums.

On the other side, patient advocates say that not requiring the coverage would hurt both individuals and healthcare providers.

“It could leave countless people with too little coverage to meet their health care needs and drive higher rates of uncompensated care at hospitals already struggling to cover their costs,” Bruce Siegel, president of America’s Essential Hospitals, said in a statement.

Earlier on Wednesday, a Freedom Caucus aide said more than 25 of its members were opposed, enough to stop the bill from passing. Republicans cannot afford to lose more than 21 votes from their own party, since Democrats are united in opposition.

Democrats, meanwhile, said amending the bill in the Senate would affect procedure, and increase the amount of votes Republicans would need in that chamber. Currently, Republicans intend to pass the plan through budget reconciliation, a process with little room for changes that only requires a simple majority to pass.

Headway

White House spokeswoman Sarah Sanders also gave signs negotiations were making headway late on Wednesday.

“We are continuing to move forward and adding new supporters constantly,” she said. “As we have indicated previously we are open to changes to the bill that make it better and grow its support.”

The primary aim of Obama’s signature legislation, passed in 2010, was reducing the numbers of Americans with no health coverage. Twenty million people gained insurance under the law.

The nonpartisan Congressional Budget Office estimated 14 million people would lose coverage under the Republican plan by next year. It also said 24 million fewer people would be insured by 2026.

The Republican plan would also rescind taxes created by Obamacare, repeal penalties for not buying coverage, slash funding for the Medicaid program for the poor, and modify subsidies that help individuals buy plans.

In the two weeks since it was unveiled, shares of some hospital operators and health insurers have fallen more than 10 percent.

If the healthcare bill passes the House, the Senate could take it up next week. Republican leaders hope that if the Senate acts quickly, the bill could go back to the House for a final vote by mid-April, possibly allowing Trump to sign it into law by Easter, April 16.

Opponents of the overhaul have been fiercely vocal, and on Wednesday protesters, many in wheelchairs or with serious medical conditions, blocked the Capitol rotunda for about an hour.

“Rather go to jail than die without Medicaid,” they chanted.

Capitol police said they made 54 arrests and later released the protesters.