Key Republican senators plan to reveal an update of their Obamacare repeal bill on Monday in the hopes of getting a vote on it by the end of the month.

Republican Sens. Bill Cassidy of Louisiana, Lindsey Graham of South Carolina, and Dean Heller of Nevada are proposing to block grant all federal healthcare dollars for the Medicaid expansion to states, along with funds equalling the value of Obamacare tax credits. The proposal has emerged as the only Obamacare repeal bill left standing after the Senate narrowly voted down a "skinny" repeal bill in late July.

Cassidy said the senators hope to reveal a new version of the bill on Monday and then send it to be scored by the nonpartisan Congressional Budget Office. Cassidy told reporters Thursday he expects a score in a matter of weeks.

But the senators face a serious time crunch to get a repeal bill voted on before the end of this week. The instructions for using reconciliation, a procedure that lets the Senate vote on a bill and pass with just a simple majority, expire at the end of this month.

"That is why I am staying up until 1 in the morning and waking up at 5," Cassidy told reporters.

It remains unclear if Cassidy and Graham have enough support for the bill.

Cassidy was heartened that Sen. John McCain, R-Ariz., appeared to endorse the measure in a report in The Hill newspaper. However, McCain issued a statement later Thursday clarifying he would have to see the final version to fully get on board with Graham-Cassidy-Heller.

McCain voted against the "skinny" repeal bill along with Republican Sens. Lisa Murkowski of Alaska and Susan Collins of Maine in late July. The bill, which gutted key parts of Obamacare, was intended to serve as a vehicle to kick-start talks with the House on a new Obamacare repeal bill.

Cassidy told reporters that if they get 50 votes for the proposal, then Senate Majority Leader Mitch McConnell would hold a vote on it.

Cassidy and Graham were both heartened by a deal reached by President Trump and Democrats to raise the debt ceiling and fund the government for three months. This avoids a messy fight that could have taken up a lot of time in September before government funding expired at the end of the month.

The deal "clears some space on the deck," Cassidy said.

Graham told reporters that the deal gives them more time and said the bill would be out very soon.

President Trump would sign the bill if it comes to his desk, White House adviser Kellyanne Conway said Wednesday on Fox News.

Cassidy said the new version of the bill will have a new formula on how to distribute the funding. Obamacare proponents say that the bill would drastically cut more than $400 billion in funding for the law's Medicaid expansion and Obamacare's tax credits.

But Cassidy said the bill will do a better job of reversing inequality in where Obamacare funding goes. "Right now, four states get 37 percent of the money spent on behalf of the Affordable Care Act," he said.

Some lawmakers are still skeptical about whether another Obamacare repeal vote can come together this month. However, if the Senate can't get something done by the end of September, which is the end of the federal fiscal year, then the Senate can always pass new reconciliation instructions this fall.

The Senate still needs to hold votes on a bipartisan Obamacare stabilization deal and legislation to reauthorize the Children's Health Insurance Program. There may also be more votes on disaster relief for people affected by Hurricanes Irma and Harvey.

In addition, the House will have to vote again on whatever comes out of the Senate.

Congress is already preoccupied with "hurricanes, the appropriations process, a couple different reauthorizations and tax reform," said Rep. Mark Sanford, R-S.C., a member of the hardline House Freedom Caucus. "I don't know how in the world you get to healthcare this month. I would love to see it but I don't see it coming."