WASHINGTON (AP) -- President Barack Obama's health care law would let several million middle-class people get nearly free insurance meant for the poor, a twist government number crunchers say they discovered only after the complex bill was signed.

The change would affect early retirees: A married couple could have an annual income of about $64,000 and still get Medicaid, said officials who make long-range cost estimates for the Health and Human Services department.

After initially downplaying any concern, the Obama administration said late Tuesday it would look for a fix.

Up to 3 million more people could qualify for Medicaid in 2014 as a result of the anomaly. That's because, in a major change from today, most of their Social Security benefits would no longer be counted as income for determining eligibility. It might be compared to allowing middle-class people to qualify for food stamps.

Medicare chief actuary Richard Foster says the situation keeps him up at night.

"I don't generally comment on the pros or cons of policy, but that just doesn't make sense," Foster said during a question-and-answer session at a recent professional society meeting.

"This is a situation that got no attention at all," added Foster. "And even now, as I raise the issue with various policymakers, people are not rushing to say ... we need to do something about this."

Administration officials said Tuesday they now see the problem. "We are concerned that, as a matter of law, some middle-income Americans may be receiving coverage through Medicaid, which is meant to serve only the neediest Americans," said Health and Human Services spokesman Richard Sorian. "We are exploring options to address this issue."

Administration officials and senior Democratic lawmakers initially defended the change, saying it wasn't a loophole but the result of a well-meaning effort to simplify the rules for deciding who would get help under the new health care law. Instead of a hodgepodge, there would be one national policy.

But Sen. Orrin Hatch of Utah, the ranking Republican on the Senate Finance Committee, called the situation "unacceptable" and said he intended to look into it.

Governors have been clamoring for relief from Medicaid costs, complaining that federal rules drive up spending and limit state options. The program is now one of the top issues in budget negotiations between the White House and Congress. Republicans want to roll back federal requirements that block states from limiting eligibility.

Medicaid is a safety net program that serves more than 50 million vulnerable Americans, from low-income children and pregnant women to Alzheimer's patients in nursing homes. It's designed as a federal-state partnership, with Washington paying close to 60 percent of the total cost.

Early retirees would be a new group for Medicaid. While retirees can now start collecting Social Security at age 62, they must wait another three years to get Medicare, unless they're disabled.

Some early retirees who worked all their lives may not want to join a program for the poor, but others might see it as a relatively painless way to satisfy the new law's requirement that most Americans carry health insurance starting in 2014. It would help tide them over until they qualify for Medicare.

The actuary's office said the early retirees eligible for Medicaid would be on top of an estimated 16 million to 20 million new people that Obama's law already brings into the program, by opening it to childless adults with incomes near the poverty level.

It's unclear how much it would cost to cover the retirees. Federal taxpayers will cover the entire initial cost of the expansion.

Republicans already see a problem.

Former Utah governor Mike Leavitt said bringing early retirees in will "just add fuel to the fire," bolstering the argument from Republican governors that some of Washington's rules don't make sense.

"The fact that this is being discovered now tells you, what else is baked into this law?" said Leavitt, who served as Health and Human Services secretary under President George H.W. Bush. "It clearly begins to reveal that the nature of the law was to put more and more people under eligibility for government insurance."

The Medicare actuary's office roughed out some examples to illustrate how the provision would work. A married couple retiring at 62 in 2014 and receiving the maximum Social Security benefit of $23,500 apiece could get $17,000 from other sources and still qualify for Medicaid with a total income of $64,000.

That $64,000 would put them at about four times the federal poverty level, which for a two-person household is $14,710 this year. The Medicaid expansion in the health care law was supposed to benefit childless adults with incomes up to 133 percent of the poverty level. A fudge factor built into the law bumps that up to 138 percent.

The actuary's office acknowledged its $64,000 example would represent an unusual case, but nonetheless the hypothetical couple would still qualify for Medicaid.

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