Republican Sen. Lamar Alexander told reporters on Tuesday that he and Democratic Sen. Patty Murray had reached a deal that would formally appropriate the cost-sharing-reduction payments introduced by the Affordable Care Act, the healthcare law better known as Obamacare.

Last week, the Trump administration said it would stop the payments because it could not legally continue to do so.

The payments help defray costs to insurers that are mandated to provide plans with low out-of-pocket costs to poorer Americans.

Here's a rundown of what the senators' preliminary plan includes, according to a congressional aide:

Fund the payments through 2019.

Restore $106 million in outreach to encourage people to sign up for plans on the individual insurance exchanges during the upcoming open-enrollment period.

Allow states to implement reinsurance programs, which help mitigate losses for insurers with assistance from the government and are designed to lower costs for consumers.

Expedite approvals for what are known as "1332 waivers," which allow states to make changes to their exchanges as long as the changes would lower costs.

Allow people over the age of 30 to sign up for catastrophic, or "copper," plans, which do not abide by the ACA's basic-coverage mandates but have cheaper premiums.

"We're ironing out a few of the last details right now, but I'm very optimistic that we'll be able to make an announcement with all the details very soon," Murray said at a press conference.

Alexander said the plan would be introduced to members of both parties on Tuesday and that he and Murray would be "seeking cosponsors of the legislation hopefully to introduce later in the week."

Republican leadership in September quashed the Alexander-Murray talks in favor of an attempt to pass legislation to overhaul the US healthcare system.

Alexander is the chairman of the Senate Health, Education, Labor, and Pensions Committee, and Murray is the ranking member.

At a press conference with Greek Prime Minister Alexis Tsipras on Tuesday, President Donald Trump endorsed the deal and said the White House was "involved" with the talks.

It is unclear whether the deal could succeed in Congress, as House Speaker Paul Ryan has said he will not bring to the floor a bill designed to stabilize the insurance exchanges.

Democratic leadership supports the plan, according to Senate Minority Leader Chuck Schumer.

"First, I want to salute both Lamar Alexander and Patty Murray for working hard on a bipartisan solution," Schumer said at a press conference. "We think it's a good solution, and it got broad support when Patty and I talked about it at the caucus at lunch today."

And Sen. John McCain, who has been a thorn in the side of Republican leadership on past healthcare attempts, praised the deal and said he would vote for it.

"As I have repeatedly stressed, health care reform ought to be the product of regular order in the Senate, and the deal reached today marks a critical step towards that end," he said.

Another GOP hold out, moderate Susan Collins, also praised the package during an appearance on Meet The Press Daily.

"I would have liked to have seen a specific authorization and some seed money for reinsurance pools, which would further help to lower premiums," Collins told host Chuck Todd. "But this is a good package, and I hope it will be passed very quickly so it can have an impact on rates this year."

Eric Assaraf, an analyst at Cowen Washington Research Group, said that with bipartisan support the plan was likely to pass, though he said it could take some time.

"We believe the market stabilization bill would likely garner enough votes for passage and would be signed into law as President Trump has expressed his desire for a short-term fix to Sen. Alexander after moving to end CSR payments last week," Assaraf wrote in a note to clients.

Conservatives have had mixed reactions.

Rep. Mark Walker, the chairman of the Republican Study Committee, said he would not support the package.

"The GOP should focus on repealing & replacing Obamacare, not trying to save it," Walker said via the committee's Twitter account. "This bailout is unacceptable."

But Rep. Mark Meadows, the chairman of the House Freedom Caucus, called it "a good start."

"Not sure it goes far enough to lower premiums, but limited-duration plans and HSA expansion might provide better conservative support," Meadows told reporters. "I certainly applaud the senators for working hard to address premiums."