Kentucky Sen. Rand Paul said Thursday that he was a "no" on his chamber's healthcare plan, slamming it as "Obamacare-Lite."
"We're a no on the bill currently," the two-term Republican told reporters on Capitol Hill. "I'm very concerned about the content.
"The most important thing is we promised to repeal Obamacare," he added. "The current bill looks like we're keeping large parts of Obamacare.
"We're keeping subsidies, boosting subsidies – and I think it looks a lot like Obamacare.
"I think we can do better than this," he said.
Paul was among four Republican senators who said that they would oppose the Senate's version of the American Health Care Act after party leaders introduced it Thursday.
The others are Sens. Ted Cruz of Texas, Mike Lee of Utah, and Ron Johnson of Wisconsin.
Republicans hold a slim majority in the Senate, 52-48, and can only afford to lose two votes on the healthcare bill.
The Senate's AHCA unveiling came weeks after Majority Leader Mitch McConnell, also of Kentucky, and other key leaders in a 13-member working group prepared the legislation in secret.
The House passed its version of the bill last month.
The Senate bill includes a slower phase-out of Obamacare's Medicaid expansion than the House version and provides more generous tax credits for lower-income people.
But the legislation is still expected to result in millions of people losing insurance when evaluated by the Congressional Budget Office.
In addition, CNN reported that Paul received a telephone call from President Donald Trump asking him to support the legislation.
"Paul actually told the president, 'Here are the problems with it' and explained the problems and told the president that he would not support the bill as is," chief political correspondent Dana Bash said.
In talking with reporters at the Capitol, Paul stated his longstanding opposition to Obamacare and called the Senate bill "Obamacare-Lite."
"I don't think there's anybody in America that's more against Obamacare as myself," he said. "As a physician, I've seen the ravages of it.
"I've traveled to 42 states running on repeal of Obamacare. I just didn't run on Obamacare-Lite.
"I didn't run on replacing it with more government programs. I didn't run on allowing the death spiral of Obamacare to continue just to subsidize with taxpayer money."
He also bashed the secretive process, saying he preferred the bill be crafted by committee and include a public hearing, and predicted a vote would not be held next week.
"We should have at least six or seven working days for this bill and that, I think, would be a minimum," he said.
"Not only do we need to read it, but we need to negotiate over what's good, what's bad and what we can get in the bill to make it better.
"I think it could take longer."