Speaker Paul Ryan confirmed on Friday that that the House may need to vote on the American Health Care Act a second time before the Senate can take up the bill, even as he stressed it was unlikely.

Republicans are using the budget "reconciliation" process to pass their health care bill, which allows them to push legislation through the Senate with a simple majority. But that depends on the bill meeting certain requirements — and one of them is that it reduces the deficit by at least $2 billion over the next decade.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

The trouble is that Republicans voted on their House bill without waiting for the Congressional Budget Office, the federal agency that evaluates legislation, to finish its projections, which will be released on Wednesday.

Bloomberg News reported Thursday and NBC News confirmed that House leaders have not formally sent their bill to the Senate on the chance that it fails to meet the deficit requirements.

"We just want to, out of an abundance of caution, wait to send the bill over to the Senate with the final score," Ryan told radio host Hugh Hewitt on Friday morning. "So we’re basically being overly cautious, but there’s really not an issue here."

A previous version of the American Health Care Act saved $150 billion over 10 years and both Ryan and some outside health experts expect the new one to maintain sufficient savings. But there were major changes to the final version that add a degree of uncertainty.

The wildcard is a new provision that would allow states to opt out of Obamacare’s requirements that insurance plans carry a minimum package of benefits as well as its rule that insurers charge customers the same price regardless of whether they have a pre-existing condition.

The first version of AHCA saved money in part by insuring 24 million fewer people than current law, meaning they would not use a tax credit in the bill that can go toward coverage. If states opt out of Obamacare’s requirements, though, millions more might be able to afford cheaper, if less generous, plans. The nonpartisan Committee for a Responsible Federal Budget estimates that if 10 million more people purchased insurance under the new version, the additional contributions to their tax credits would add $300 billion in costs.

If that happens, the House would have to vote again on changes, bringing them back to a politically charged bill that they barely carried over the finish line in a narrow 217-213 vote.