WASHINGTON (AP) -- The Obama administration defended the health care overhaul in a filing Friday with the Supreme Court that calls the law an appropriate response to a "crisis in the national health care market."

The administration filed a written submission in the high court's biggest case this term, with the potential to affect President Barack Obama's bid for re-election.

The government called on the court to uphold the core requirement that individuals buy insurance or pay a penalty. One federal appeals court struck down the so-called individual mandate as exceeding Congress' power under the Constitution. But two other federal appeals courts upheld the law and agreed with the administration's argument that Congress was well within its power to adopt that requirement.

Florida and 25 other states, as well as the National Federation of Independent Business, told the court in separate briefs that if the justices strike down the individual requirement, they should invalidate the rest of the law as well. Thirty-six Republican senators echoed the states' argument in their own filing.

The law is aimed at extending health insurance coverage to more than 30 million previously uninsured people and would, by 2019, leave just 5 percent of the population uninsured, compared with about 17 percent today, according to the Congressional Budget Office. About half of the increase would come from the individual requirement; the rest would come from an expansion of Medicaid and other provisions.

The health care law has attracted intense opposition from Republicans, including the party's presidential candidates, all of whom have vowed to repeal it if elected. The individual insurance requirement has been a particular lightning rod because it forces people to buy a product from a private insurer whether they want to or not, or pay a penalty for failing to do so.

This provision was struck down by a divided panel of the Atlanta-based 11th U.S. Circuit Court of Appeals, the only appeals court that has ruled against the law among the four appeals courts that have considered it. One appeals court held that it was too soon to rule on the law.

But the administration said the requirement falls within Congress' power under the Constitution's Commerce Clause because health care is an issue of supreme national importance that consumes nearly 18 percent of the U.S. economy.

People may lack insurance, but they still get health care, and the costs get passed on the insured, the administration said.

"Congress found that the cost of tens of billions of dollars in uncompensated care provided to the uninsured is passed on to insured consumers, raising average annual family premiums by more than $1,000," the administration said.

The individual mandate also goes hand-in-hand with another part of the law that prohibits insurers from denying coverage to people with existing medical conditions or hiking their premiums, the administration said.

Separately, the insurance industry reinforced this point to the court, arguing that it needs the larger pool of people so that it can afford to cover people regardless of their medical history.

America's Health Insurance Plans and the BlueCross BlueShield Association - major trade groups - said in their court papers that if the individual requirement is struck down, the ban on denial of coverage based on pre-existing medical conditions must also go. Otherwise, premiums will rise and healthy people will drop coverage. The groups did not take a position on the constitutionality of the law.

Additional briefs due later in January and next month will address other aspects of the law. A decision should come by late June.

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