 -- House Republicans, who have spent the last two weeks quietly negotiating a GOP health care proposal, on Thursday floated a carefully crafted amendment to the bill that failed several weeks ago, and some say it could be the key to getting the measure passed.

Details of the proposal were first reported by Politico.

The new activity encouraged President Trump, who expressed optimism that the House could pass the "great bill" as early as next week — though senior GOP aides downplayed that possibility.

The proposed amendment comes from moderate Rep. Tom MacArthur, R-N.J., who has led talks on tweaking the health care bill with House Freedom Caucus Chairman Mark Meadows. It would make essential health benefits — requiring plans to cover things like prescription drugs, maternity care and mental health services — the federal standard but offer limited waivers to states that want to do things differently and can prove that doing so would lower the cost of health care or increase coverage.

States could also apply for limited waivers from the community rating provision of Obamacare — which requires insurers to cover people with existing conditions — as long as those states create and fund a high-risk coverage pool for affected consumers.

The waiver would effectively undermine Obamacare's existing conditions mandate, according to health care experts, because it would nullify the requirement that insurers offer coverage in a given area at the same price, regardless of health status.

With the 100-day mark of the Trump administration on the horizon, the White House is eager for a legislative victory on health care. Senior White House aides and Vice President Mike Pence led talks with House Republicans on Capitol Hill two weeks ago that laid the groundwork for the new proposed amendment.

But on Capitol Hill, there is no indication that the legislative dynamics have shifted since the GOP health care bill was pulled from the floor last month. The proposal has not been finalized, and does not yet have the approval of GOP leaders, who remain focused on reupping government funding before it runs out next Friday.

Asked Thursday if he wants to see the House pass the GOP health care bill or pass a measure to fund the government and prevent a partial shutdown next week, President Trump said "both."

"We're doing very well on health care," Trump said in news conference with Italian Prime Minister Paolo Gentiloni.

"We have a good chance of getting it soon," he said. "I would like to say next week, but it will be ... I believe we will get it, and whether it is next week or shortly thereafter."

While members had not seen legislative text for the new proposal as of Thursday afternoon, Rep. Dave Brat, R-Va., a member of the far-right House Freedom Caucus that largely opposed the first version of the GOP health care bill, said in an interview that the proposed amendment “looks very promising” to his caucus.

“I think it’s doable,” he said of a vote. “It would tee up the budget process and tax reform and it’s very needed.”

A House Republican source said it’s unlikely the measure will attract any new support from the moderate wing of the House Republican conference. If anything, additional moderate members could pull support for the bill given the implications for coverage of existing conditions.

House Republicans have a conference call scheduled for Saturday where members will be briefed on the latest health care and government funding developments. Members return to Washington next Tuesday, and have until Friday night to pass a funding measure and avert a government shutdown.