WASHINGTON ― Nevada Gov. Brian Sandoval (R) warned Congress on Wednesday about the consequences of repealing the Affordable Care Act without an adequate replacement for millions of people insured under the law.

Sandoval, who opted to expand Medicaid under Obamacare for Nevada’s neediest residents, said he likes what he’s heard so far about a replacement for the law. But the governor added there are “a lot of lives at stake” with its possible repeal and said he hoped congressional leaders would take them into consideration.

“We have a state run insurance exchange. It’s working well for us. There are a lot of lives at stake, with regard to decisions that are made here,” Sandoval said at an event hosted by the National Governors Association near Capitol Hill.

“I hope decisions aren’t made in a vacuum and that there is a reach out to the governors. Everything can be improved,” he added of the law. “The rhetoric I’ve heard is nobody’s going to lose their coverage, that prices aren’t going to increase. I say great, that’s wonderful. But until we get into the specifics, I’m not going to get into an adversarial relationship.”

The governor noted he had conveyed his concerns to the entire Nevada delegation, including Republican Sen. Dean Heller, who supports repealing the law.

Sandoval is one of five GOP governors ― including Govs. Charlie Baker of Massachusetts, Rick Snyder of Michigan, John Kasich of Ohio and Asa Hutchinson of Arkansas ― who set a letter to Congress about the disastrous consequences of repealing a law without a replacement in place.

Earlier this month, Senate Republicans took the first big step in their years-long crusade against the law. They say they want to ensure those people currently insured through the law wouldn’t be hurt by efforts to replace it. Rep. Tom Price (R-Ga.), who is President Donald Trump’s nominee to lead the Department of Health and Human Services, for example, says it is “absolutely imperative” that people with insurance get to keep their coverage even if Republicans repeal Obamacare.

But current GOP proposals to replace the law ― such as block grants ― would result in far less federal spending on health care and thus far fewer insured people.

“In Virginia, unfortunately, we have not expanded Medicaid. A repeal of the ACA, accompanied by a proposed block grant, could cost the state of Virginia in the next budget over $300 million,” said Virginia Gov. Terry McAuliffe (D), the chair of the NGA, who spoke alongside Sandoval at the event.

McAuliffe said that House Speaker Paul Ryan (R-Wis.) disclosed few details about the GOP replacement for Obamacare in his meeting with governors earlier on Wednesday.

“Nobody today is telling us what they’re going to replace it with,” he said. “I don’t think anybody knows, to be honest with you.”

But he added the sense he got from the speaker about giving more power to states, is that Ryan would like to see them implement block grants.