Senate conservatives are growing worried that the Senate Republican healthcare reform legislation will exclude a proposal to give health insurers the option of selling cheaper plans, an option conservatives are demanding in order to ensure that the bill helps drive down insurance costs.

The Consumer Freedom Act, sponsored by Sens. Ted Cruz, R-Texas, and Mike Lee, R-Utah, would allow health insurance companies to offer less expensive plans that do not include Obamacare's essential health benefits, as long as they provided at least one plan that includes them.

According to Republican aides, only an outline of the Cruz-Lee proposal was sent to the Congressional Budget Office for analysis, which suggests that the GOP leadership isn't serious about including it in the final bill. GOP leaders are hoping to bring to the floor for a vote as early as next week.

"Senate leadership was given full text of the CFA the Friday before July 4th," a leadership aide told the Washington Examiner. "But CBO was only given bullet points. We have since diligently responded to all of CBOs questions about the text."

The Cruz-Lee amendment has drawn criticism from healthcare experts who say it will hurt those with pre-existing conditions because it could prompt more people to choose the cheaper insurance. That would change the risk profile of the people who still want the Obamacare-compliant insurance, and drive up the price of those plans, which could put insurance out of risk for people with pre-existing conditions.

Those drawbacks, Republican aides have said, could make a healthcare reform measure harder to pass in the Senate because many GOP lawmakers would oppose any provision that would effectively cause those with pre-existing conditions to be shut out of the marketplace.

The Cruz-Lee amendment has won the backing of President Trump and outside conservative groups, including the Club for Growth, as well as the House conservative faction, the Freedom Caucus.

"We are going to continue to talk and listen and exchange ideas on how we can continue to make improvements," Senate Majority Whip John Cornyn, R-Texas, said.

Senate Majority Leader Mitch McConnell, R-Ky., said Monday that Republicans "will continue working" on a health care bill but did not schedule a vote.

People familiar with the negotiations told the Washington Examiner that Republican leaders hope to hold a vote on legislation as early as next week, and could reveal the details of the proposal to Republican Senators on Tuesday afternoon.

Sen. Pat Toomey, R-Pa., said on CNBC Monday that the revised bill would include $45 billion in additional funding for states to deal with the opioid epidemic.

Toomey also cited "a big push to have a change in the regulatory mandates, so that we can have the lower premiums that we're looking for… and more control and more choices that will appeal to the conservatives."

The bill may also maintain Obamacare's 3.8 percent investment income tax thanks to the demands of Republican lawmakers who don't like the idea of cutting taxes for the upper-income earners while reducing Medicaid.