WASHINGTON » A small-business group opposed to the health care overhaul is asking the Supreme Court to strike down the entire law, not just the core requirement to buy health insurance or pay a penalty.

The National Federation of Independent Business filed an appeal Wednesday of a portion of the ruling by the federal appeals court in Atlanta that struck down the individual insurance requirement.

The appeals court upheld the rest of the law, an outcome the NFIB says is bad for business. The law would extend coverage to more than 30 million people who are now uninsured, many through subsidies to purchase private insurance and an expansion of Medicaid.

The business filing comes the same day the Obama administration’s response is due at the Supreme Court in another challenge to the same law. In that case, the federal appeals court in Cincinnati upheld the law.

The NFIB pursued its lawsuit along with 26 states. The states are expected to pursue a high court appeal challenging the legitimacy of the Medicaid expansion.

In court papers filed Wednesday, the NFIB said the individual insurance mandate was at the heart of the health care law’s "carefully crafted compromise."

The administration itself said in the Atlanta-based 11th U.S. Circuit Court of Appeals that reforms in the insurance market, including requiring insurers to cover people without regard for pre-existing health conditions, would not work without the mandate.

The insurance requirement is intended to force healthier people who might otherwise forgo insurance into the pool of insured, helping to reduce private insurers’ financial risk.

The business group also stressed the importance of resolving the overhaul’s constitutionality as soon as possible, which under normal court procedures would be by June 2012. While a decision in that time frame would come in the midst of the 2012 presidential campaign, the NFIB said it is more important to resolve uncertainty about costs and requirements than drag out consideration into 2013 or beyond.

"When you talk to our members and other small-business owners about what is the biggest problem they’re facing, they say uncertainty," said Karen Harned, executive director of the NFIB’s legal division. "When you ask what, one of first answers is the health care law."

In addition to the competing rulings on the law’s validity, a federal appeals court in Richmond ruled that it is premature to decide the law’s constitutionality. Citing a federal law aimed at preventing lawsuits from tying up tax collection, that court held that a definitive ruling could come only after taxpayers begin paying the penalty for not purchasing insurance.

The federal appeals court in Washington also heard arguments in yet another lawsuit against the overhaul last week. That court has no timetable for its decision.