Republican senators are still working to revive an Obamacare repeal bill even though some in their own party are starting to doubt anything can be done.

The Senate and White House are trying to pick up the pieces after a humiliating defeat last week of a bill aimed at kickstarting talks with the House on Obamacare repeal. But, as some senators are meeting with the White House to write a new proposal, other Republicans are not optimistic they can get anything done this summer, if at all.

Sen. Chuck Grassley, R-Iowa, didn't mince words when asked about how hopeful he is if anything can get done on healthcare reform.

"Right now I'm very pessimistic," he said.

Sen. Orrin Hatch, R-Utah, told Reuters Monday he and other senior Republicans plan to tell President Trump to move on to tax reform, even though he hasn't given up on healthcare reform.

"There's just too much animosity and we're too divided on healthcare," he said.

Trump and White House officials have not given up on Obamacare repeal after the defeat. Trump tweeted over the weekend that Republican senators would be "total quitters" unless they take up healthcare again.

White House Budget Director Mick Mulvaney said Sunday the Senate shouldn't vote on anything else until it votes again on healthcare.

And some in the Senate aren't giving up hope. Sen. Bill Cassidy, R-La., held a listening session on Monday with Health and Human Services Secretary Tom Price and governors on the proposal. Centers for Medicare and Medicaid Services Administrator Seema Verma also attended, according to a White House aide.

One idea being discussed is to block grant to states the funding for the Medicaid expansion and tax credits to purchase coverage on Obamacare's exchanges. The proposal would repeal some of the law's taxes and eventually phase out the enhanced federal matching funds for Medicaid.

Cassidy and Graham put together the proposal a few weeks ago with the hopes of adding it to a Senate replacement bill called the Better Care Reconciliation Act. However, the Senate voted down that replacement bill last week alongside another bill that repeals Obamacare.

Some senators were optimistic about the Graham-Cassidy approach. Sen. Mike Rounds, R-S.D., said the proposal could be taken up as a standalone bill or it could make some additions such as amendments from Sen. Rob Portman, R-Ohio, and Sen. Ted Cruz, R-Texas.

Portman's amendment would add $100 billion in Medicaid funding and let states borrow funds from tax credits and a stability fund to blunt the effect of cuts to Medicaid funding.

Cruz's amendment would let states sell plans that don't comply with Obamacare's insurer regulations as long as it sold one plan that does. Hardline conservatives have clamored for including repeal of Obamacare's insurer regulations in health reform because of their impact on premiums.

A spokesman for conservative Sen. Mike Lee, R-Utah, said he is reviewing the proposal but to earn his vote it must include regulatory relief.

But there are plenty of unanswered questions about the proposal that might not be solved by next week.

Right now the Senate is awaiting a score from the Congressional Budget Office on the proposal, said Sen. John Thune, R-S.D., who is the third-ranking senator in GOP Senate leadership. He added it could take a while.

"Most of these new ideas take them a couple of weeks at least to score. On this one since it is plowing some new ground it may take a while," he said. "We are anxious to get that information back."

The CBO is also in the midst of scoring the Cruz and Portman amendments too. But senators are itching to get something done to try and stabilize markets.

"We have to continue working on it because come Jan. 1 we are going to see a huge increase in premiums and I think the (individual) market will continue to deteriorate with Obamacare in place," Rounds said.

Some states have announced high rate hikes in part because of uncertainty over whether the Trump administration would fund cost-sharing reduction payments to insurers. The payments reimburse insurers for lowering out-of-pocket costs for low-income people on Obamacare.

Democrats have called for a bipartisan solution that includes new money for reinsurance, which covers the sickest claims from insurers.

However, Rounds recoiled at doing any short-term fix such as reinsurance, saying that a more comprehensive approach is needed.

"A short-term, just put money in simply will not work," he said. "Unless we fix the overall plan then we will be looking at that continuously month after month with no end in sight."

Other senators weren't so keen on giving up on Obamacare repeal, despite the time constraints.

"Giving up is permanent. Getting defeated is just temporary," said Sen. John Kennedy, R-La.

Al Weaver contributed to this story