WASHINGTON (AP) — Republican leaders added a penalty for people who've let their insurance lapse Monday as party leaders prepared to begin pushing their health care measure through the Senate, despite a rebellion within GOP ranks.

Under the new provision, people who've had at least a 63-day gap in coverage during the past year and then buy a policy would face a six-month delay before it takes effect. Until now, the measure that Senate Majority Leader Mitch McConnell, R-Ky., introduced last week included no language prodding healthy customers to purchase insurance.

The change is aimed at helping insurance companies and the insurance market by discouraging healthy people from waiting to buy a policy until they get sick. Insurers need healthy customers who are inexpensive to cover to help pay the costs of people with medical conditions that are costly to treat.

The Senate bill would roll back much of President Barack Obama's health care overhaul. His statute pressures people to buy insurance by imposing a tax penalty on those who don't, but the Republican legislation would repeal that penalty, effectively erasing Obama's so-called individual mandate.

The House approved its legislation in May. It would require insurers to boost premiums by 30 percent for those whose coverage lapsed.

Senate Minority leader Chuck Schumer, D-N.Y., criticized Republicans for penalizing people who might have had coverage gaps because of losing a job or temporary financial problems.

"It's the epitome of 'mean' to say that those without health insurance for several months have to wait even longer to get it," said Schumer, repeating a word President Donald Trump used to describe the House version of the bill.

The Senate plan would phase out extra federal money 31 states receive for expanding Medicaid to additional low-income earners, and put annual caps on overall Medicaid money the government until now has automatically paid states, whatever the costs. It would let states ease requirements that insurers cover certain specified services like substance abuse treatments. It would also reshape federal health care subsidies for people buying individual policies and eliminate taxes on wealthier people and medical companies that Obama's law used to expand coverage.

The American Medical Association used a two-page letter to lambast the Senate legislation. The organization, which represents many of the nation's doctors, said the legislation would likely produce skimpier subsidies and fewer benefits for consumers, and "will expose low and middle income patients to higher costs and greater difficulty in affording care."

McConnell is expected to offer other changes to his proposal as he seeks to nail down support for the package. He can win approval only if he limits Republican no votes to just two of the 52 GOP senators, since Democrats solidly oppose the bill. Debate should begin as early as Tuesday.

Five GOP senators — four conservatives and a moderate — have said they oppose the measure McConnell unveiled last week. Others from both ends of the party's spectrum have expressed concerns, complicating McConnell's task because edging the bill in one direction risks alienating GOP lawmakers from the other side.

None of the dissident senators have ruled out supporting the legislation if it is revised.

Earlier Monday, one of the conservatives used unusually harsh terms to accuse party leaders of trying to rush the party's health care bill through the Senate.

"They're trying to jam this thing through. It is far from a perfect bill," Sen. Ron Johnson, R-Wis., told conservative talk radio host Hugh Hewitt. Johnson called leadership's effort "a little offensive" and said conservatives had no input into the package.

McConnell drafted the plan behind closed doors after numerous meetings among GOP senators.

Moderate Sen. Dean Heller, R-Nev., has also said he's against the proposal, and several others from both wings of the party have expressed qualms. Heller faces a competitive re-election race next year.

In an opinion column in Monday's New York Times, Johnson wrote that McConnell's initial draft "doesn't appear to come close" to the goal of making coverage more affordable. He criticized the measure for increasing federal spending on subsidies for people buying coverage and not eliminating enough of Obama's regulations on insurers, including protections for consumers with pre-existing medical conditions.

In another important dynamic, lawmakers were awaiting a key analysis from the nonpartisan Congressional Budget Office of the measure's price tag and the number of people who might lose coverage if it is enacted. The new report was expected as early as Monday.

The Senate legislation resembles a bill the House approved in May that the budget office said would result in 23 million additional Americans without coverage by 2026.

President Donald Trump continued his attacks on congressional Democrats on Twitter Monday, saying: "The Democrats have become nothing but OBSTRUCTIONISTS, they have no policies or ideas. All they do is delay and complain. They own ObamaCare!"

The other three GOP conservatives who say they're against the legislations are Sens. Rand Paul of Kentucky, Mike Lee of Utah and Ted Cruz of Texas. They say the bill doesn't go far enough if repealing Obama's 2010 statute.

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Associated Press writer Steve Peoples in Colorado Springs, Colorado, contributed to this report.