While Ryan said he felt "very good" about the health bill's prospects in the House, a leading conservative lawmaker, Representative Mark Meadows, told the C-Span "Newsmakers" program that there were currently 40 Republican "no" votes in the House. Republicans hold a majority in the chamber but cannot afford to have more than 21 defections for the measure to pass.

Meadows and two other Republican opponents of the bill, Senators Mike Lee of Utah and Ted Cruz of Texas, met at Trump's Mar-a-Lago estate in Florida on Saturday "negotiating with the president's team, trying to fix this bill," Cruz told CBS' "Face the Nation."

North Carolina Republican Meadows said the changes being considered for the Medicaid program would not go far enough if they left it up to states to decide whether to put in place a work requirement.

Price acknowledged the tough negotiations, telling ABC's "This Week": "It's a fine needle that needs to be thread, there's no doubt about it."

The healthcare bill would face significant challenges in the Senate even if it were to pass the House.

Senator Tom Cotton, a conservative Arkansas Republican, said the bill would not reduce premiums for people on the private insurance market. "It's fixable, but it's going to take a lot of work," Cotton said on CNN's "State of the Union."

Moderate Republicans have also expressed concerns about the bill, and their worries are often not the same as that of conservatives.

Speaking on NBC's "Meet the Press," Republican Senator Susan Collins of Maine worried the bill would harm older Americans, and shift Medicaid costs to states - something critics say a block-grant approach would only make worse.

Collins said coverage issues must also be dealt with, citing a report from the Congressional Budget Office that said 14 million people would lose health coverage under the House bill over the next year and 24 million over the next decade.

Affordability has been one of the bigger concerns that insurers and hospital groups have raised about the legislation. To the extent that a change in tax credits makes healthcare more affordable for some people, insurers and hospitals could stand to benefit.

The BlueCross BlueShield Association emphasized the need for the replacement to be affordable when the draft of the healthcare bill was released earlier this month. The association represents BCBS insurers that cover the vast majority of the roughly 10 million people enrolled in 2017 Obamacare plans.

Reuters