Two Republican senators introduced a detailed bill Monday that would allow some states to keep former President Barack Obama's health care law, the Affordable Care Act, in place, while allowing others to craft their own plan.

Sen. Susan Collins, R-Maine, and Sen. Bill Cassidy, R-La., presented the bill, called the Patient Freedom Act of 2017, in a press conference Monday. The bill would give states the option to keep subsidies from the federal government that help people pay for health insurance and to receive Medicaid dollars expanded to low-income residents.

"Republicans think that if you like your insurance you should keep it, and we mean it," Cassidy said.

His statement invoked the one Obama made about his signature health care law years ago, when he said his health care law would allow patients to keep their doctors if they liked them.

Republicans have been under pressure to come up with a replacement plan for the Affordable Care Act as they are moving swiftly to dismantle it amid concerns that their choices could threaten people's finances and health. It's unclear to what extend other Republicans will back the bill, also sponsored by Sens. Shelley Moore Capito, R-W.Va., and Johnny Isakson, R-Ga. Several other lawmakers are likely to introduce their own plans in coming months, but the latest bill shows one of the options that will be debated, or hints at portions that could be included in a final plan.

"I recognize that our bill is not perfect," Collins said. "It is still a work in progress. I expect we’ll get many ideas for further refinements and we are completely open to that."

The bill would repeal the individual mandate under Obamacare that obligates people to obtain coverage or pay a penalty, while keeping popular provisions like allowing children to stay on their parents' health care plan until the age of 26 and banning insurers from refusing coverage to people with pre-existing conditions.

Collins, a moderate Republican who has long called for details of a replacement plan, said she hoped their proposal might even attract bipartisan support, while Cassidy said he believed it met the criteria President Donald Trump has outlined in previous interviews and public statements.

Democrats, now outnumbered in the House and Senate and facing a president who has vowed to undo Obamacare, have been resistant to work with Republicans on any proposals that they say could undo the protections provided by the Affordable Care Act.

It's unclear what the effect of the bill would be because it hasn't been independently evaluated by the nonpartisan Congressional Budget Office, but groups that support Obamacare were immediately critical of the Collins-Cassidy bill.

"Contrary to the rhetoric of Sens. Cassidy and Collins, you would not be able to keep your Obamacare if you like it," Topher Spiro, vice president for health policy at the liberal think tank Center for American Progress, said in a statement. "If you happen to live in a state controlled by those who oppose Obamacare, they would be able to gut your coverage and uproot Obamacare root and branch. It’s unconscionable that access to quality health care would depend on where you happen to live."

Families USA, a group that helped people sign up for coverage under Obamacare, said the Collins-Cassidy bill would result in millions losing insurance, send prices soaring and provide fewer resources to states.

“This is not a true replacement bill," Ron Pollack, the group's executive director, said in a statement. "It’s not even the true Republican replacement plan. And it falls way short of providing the protections and coverage people have under the Affordable Care Act."