WASHINGTON — A new bipartisan congressional health care plan to halt premium hikes and temporarily prop up the Affordable Care Act faltered on Wednesday after President Trump tweeted his disapproval.

A day after signaling support for the plan developed by Sens. Lamar Alexander, R-Tenn., and Patty Murray, D-Wash., Trump tweeted Wednesday that the agreement's two-year extension of subsidies for insurers to cover low-income clients might benefit insurance companies too much.

Even as the deal's supporters continued to pursue co-sponsors, its momentum slowed.

House Speaker Paul Ryan's press secretary, Doug Andres, said in a Wednesday statement, "The speaker does not see anything that changes his view that the Senate should keep its focus on repeal and replace of Obamacare."

In the Senate, some key Republicans also cast doubt on its prospects.

"I don’t agree with it," said Senate Finance Chairman Orrin Hatch, R-Utah. "I think (Alexander's) trying to do a good thing, but it’s only temporary and it leads us down a primrose path that we don’t want to go."

Republicans spent their conference luncheon discussing tax reform rather than health care, said Wyoming Sen. John Barrasso, a former orthopedic surgeon who chairs the Senate Republican Policy Committee.

"This really didn't even come up," Barrasso told reporters.

Murray and Alexander have been drafting a bill for several months to boost the insurance marketplace, but the effort took on new urgency last week when Trump announced he would no longer fund the subsidies without congressional action.

Read more:How the Alexander-Murray bipartisan health care proposal could affect you

After a phone call with Trump, Alexander indicated the deal may still have a chance and tweeted that he will work with the president to strengthen the bill's language ensuring that subsidies benefit consumers and not insurers.

But Trump's reversal on the compromise drew the ire of Senate Minority Leader Chuck Schumer of New York, who accused him of obstruction, pandering to the extreme right out of “blatant fear” and “zig zagging” on policy so that “it’s impossible to govern.”

Schumer said Trump’s tweet shows he has no understanding of the deal, which will help keep premiums down.

“It doesn’t bail out the insurance companies,” he said. “It helps people who are sick and who need health care.” Schumer added, “We should have a president who actually knows the facts of bills he talks about.”

As Alexander and Murray finalized their proposal on Tuesday, Trump seemed to indicate support for it, saying it would "get us over this intermediate hump" as Republicans work on an overall repeal-and-replace of President Obama's health care law. But he later told the Heritage Foundation, "Congress must find a solution to the Obamacare mess instead of providing bailouts to insurance companies.”

White House press secretary Sarah Huckabee Sanders said Wednesday that Trump wants to lower premiums, drive competition and provide greater flexibility to states, and the Alexander-Murray proposal doesn't go far enough to provide "relief" for all Americans.

"We think that this is ... a good step in the right direction," Sanders said. "This president certainly supports Republicans and Democrats coming to work together. But it's not a full approach and we need something to go a little bit further to get on board."

Democrats believe Republicans backing away from the deal can only hurt them in elections. But conservatives want to focus on repealing and replacing Obamacare and view the Alexander-Murray deal as an expansion of it, making the prospects of House passage difficult if Ryan were to bring it up for a vote.

The House passed legislation earlier this year to repeal Obamacare, but the Senate could not get the 50 Republican votes needed to pass any of several repeal/replace bills GOP leaders offered.

"To pass the House, we’re going to need more than Alexander-Murray," said Sen. Ron Johnson, R-Wis.

Johnson said he is talking with Alexander about including greater deductions for health savings accounts and not enforcing employer mandates.

Barrasso said he's in favor of some of Johnson's proposals.

"I support the continuation of the work to the point where it’s something the president would encourage," Barrasso said.

The deal's Senate supporters will pursue an even number of bipartisan co-sponsors to help build pressure for a vote, regardless of Trump's position, Schumer told reporters Wednesday. Once co-sponsors are lined up, Schumer said he'll ask Majority Leader Mitch McConnell, R-Ky., for a vote.

"If that happened, I would be quite certain it would pass ... and then there would be pressure on the House," he said. "If the president will come out strongly for the bill and stick to that, that will help us get it through the House."

Alexander also said Trump and the House will have to consider the agreement once more senators are on board.

"My guess is that it will become law in some form by the end of the year because the American people will not want to create chaos in the health insurance market for millions of Americans who have skyrocketing premiums, and in some cases, can’t buy insurance at all," he said.

Republicans who support the deal include Sen. John McCain of Arizona, who cast a deciding vote against the GOP's last health care proposal. He said that while he may not like the outcome, he will tell his colleagues "it's a good solution" following a bipartisan process that he supports.

But Senate Republican Conference Chairman John Thune of South Dakota was uncertain about the deal's prospects and Alexander's ability to meet Trump's demands.

"We’ll see what they can come up with," he said. "But it sounds like, there’s the president, and obviously there’s passage in the House too, and I think at this point it’s just kind of an open question."