"I will study the bill to determine whether it fulfills President Trump's campaign promises to lower premiums, maintain coverage and protect those with preexisting conditions without mandates", he said.
Budget reconciliation would allow Senate Republicans to pass their healthcare overhaul with only 50 votes, as opposed to the 60 required for normal legislation, allowing the GOP to avoid a Democratic filibuster.
Five Republican senators have announced they will not support the bill, which is created to repeal and replace Obamacare, in its current form.
"It's going to be very hard to get me to a yes", he said, noting that conservative Republican senators would likely be reluctant to add spending back to the measure.
"We have to stop this bill from becoming law", Casey said as he held up the bill Friday to a chorus of cheers and applause.
The 142-page Senate health care bill revealed Thursday was written in secret by 13 white men with little or no expertise on health care issues and no advice from doctors, hospitals or health economists, let alone from the public.
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Sens. Dean Heller of Nevada, facing a competitive 2018 re-election battle, Rob Portman of OH and Shelley Moore Capito of West Virginia expressed concerns about the bill's cuts to Medicaid and drug addiction efforts. "It does the most damage through a radical restricting of Medicaid. that will cause families to lose care", U.S. Rep. Kathy Castor, a Democrat representing the Tampa area, said during a Thursday telephone press conference.
About 20 percent of all Americans and 40 percent of America's kids get their health care through the federal government's Medicaid program. Some lawmakers are already raising concern that the bill could aggravate the problem of healthy people going without insurance, driving up costs for everyone else.
Caroline Pearson, a senior vice president of the consulting firm Avalare Health, said the Senate subsidies would be smaller than Obama's because they're keyed to the cost of a bare-bones plan and because additional help now provided for deductibles and copayments would eventually be discontinued.
Trump later criticized the House bill privately as "mean" and this week called for a health plan "with heart". Susan Collins of Maine, Lisa Murkowski of Alaska, Rob Portman of OH and Shelley Moore Capito of West Virginia, have voiced concerns similar to Heller's about the depth of the bill's Medicaid cutbacks and its impact on opioid treatment.
The House approved its version of the bill last month.
McConnell is pushing for a vote as early as next week after the bill gets a score from the congressional budget office. The group praised the bill's extra funding for insurers as well. The enhanced federal financing that pays for the expansion would disappear entirely in 2024.
AP writer Regina Garcia Cano reported from Las Vegas.