WASHINGTON (AP) — GOP frustration burst into the open Thursday over President Donald Trump's erratic response to a bipartisan health deal, even as the agreement's authors announced a list of co-sponsors in an attempt to win over the president and Senate GOP leaders.

Republican Sen. Lamar Alexander of Tennessee and Democratic Sen. Patty Murray of Washington appeared together on the Senate floor to announce 24 co-sponsors, divided evenly between Republicans and Democrats, for their deal aimed at stabilizing insurance markets and lowering premiums over the next two years.

The agreement is an effort to step into the breach after Trump announced an end to federal payments under the Affordable Care Act that go to insurers so they can reimburse out-of-pocket costs for low-income consumers. Absent congressional action, premiums for some buyers in the individual market are likely to skyrocket.

"Unless they are replaced with something else temporarily, there will be chaos in this country and millions of Americans will be hurt," Alexander said. "The president says there should be no bailout of insurance companies — no bailout of insurance companies. I agree 100 percent."

Alexander described speaking with Trump over the phone, and how the president encouraged him to move forward with a bipartisan solution. When it was released earlier this week, the president initially reacted favorably, but then he changed his tune and began condemning the deal as a bailout. The president's varying responses frustrated lawmakers of both parties, and his ultimate apparent opposition appears to have stalled the deal, perhaps permanently.

Questioned in the Oval Office on Thursday, the president again sounded lukewarm and noncommittal.

"I like people working on plans at all times. I think, ultimately, block grants is the way to go," Trump said, apparently referring to a recent GOP health care bill that took a much more sweeping approach and repealed portions of "Obamacare," but was not able to garner the support to move forward.

"Various states really wanted that block grant money. And for the most part, I think we have the votes for that," Trump said, an incorrect assertion he's made repeatedly. "There will be a transition period, so anything they're working on will be short term. It'll be absolutely short term because, ultimately, we will be — it's going to be repeal and replace," Trump went on.

Trump added that he has "great respect" for Alexander and Murray. "What I did say though is, I don't want the insurance companies making any more money ... than they have to."

Senate Republican leaders announced that Trump will join them next Tuesday at their regular weekly policy lunch.

GOP Sen. Ron Johnson of Wisconsin gave voice to frustration with the president's inconsistent response.

"It's always best for the president to be completely consistent in terms of what he's supporting or not supporting," Johnson told reporters at the Capitol. "And let's face it, he's not been particularly consistent here."

Johnson said that inaccurate rhetoric about the deal, from Trump and others, has harmed prospects for the legislation.

"It's unfortunate what's happened over the last day in terms of the rhetoric from all points. 'Bailing out insurance companies' — insurance companies get protected either way," Johnson said. "It'd be nice to get the truth out there."

Insurers will pass along increased costs to consumers. And Trump's move to cut off the payments won't save the treasury money, either, since under the Affordable Care Act the federal government will have to come in with a different subsidy to defray higher premiums for certain consumers.

The payments Trump cut off reimburse insurance companies for lowering co-payments and deductibles for about 6 million lower-income customers, which the companies must do under former President Barack Obama's law.

Without those funds, insurers would likely boost premiums by an average 20 percent, the nonpartisan Congressional Budget Office has projected. This would especially hit many buying their own health insurance who make too much to qualify for tax credits that help reduce premiums for lower earners. But the subsidy for premiums is designed to increase with the rising price of insurance, so government spending to subsidize premiums would jump.

The Alexander-Murray agreement extends the payments for two years, combined with a host of measures to give states additional flexibility under Obama's law, and a provision to allow consumers of any age to buy into a low-cost catastrophic coverage plan.

The payments in question have been in dispute since Obamacare passed, with Republicans successfully challenging them in court as an unconstitutional executive power grab of Congress' power of the purse.