WASHINGTON — On the third and final day of Supreme Court arguments over President Obama’s health care overhaul law, several justices on Wednesday indicated a reluctance to pick and choose among the law's other provisions should the requirement that most Americans have health insurance be struck down.


The questions from the justices indicated that at least some of them were considering either striking down just the requirement or the entire law.


Paul D. Clement, representing 26 states challenging the law, urged the court to overturn the entire law. Edwin S. Kneedler, a deputy solicitor general representing the Obama administration, took a middle ground, asking the court to remove the mandate and only a couple of other provisions.


A third option, supported by neither side, would be to remove only the mandate, potentially leaving Congress to grapple with the remainder of the law. The court appointed a Washington lawyer in private practice, H. Bartow Farr III, to present this argument.


The issue before the justices on Wednesday took on practical urgency after some of the questioning on Tuesday suggested that the law’s core provision, often called the individual mandate, may be in peril. It requires most Americans to obtain insurance or pay a penalty.


“My approach would be to say that if you take the heart out of this statute,” Justice Antonin Scalia said, “the statute’s gone.”


Justice Scalia, who suggested that the the whole law would have to go, appeared to go further than some of the other justices, but many of them expressed skepticism that the the rest of the law could remain intact if the court ruled the mandate to be unconstitutional.


Justice Ruth Bader Ginsburg called the court’s task, should the key provision fall, a choice between “a wrecking operation” and “a salvage job.”


Mr. Kneedler, representing Mr. Obama’s position, argued that should the court overturn the mandate two other provisions – one forbidding insurers from turning away applicants and the other barring them from taking account of pre-existing conditions – would also have to fall.


Without the mandate, administration officials say, it would be unreasonable to expect health insurers to cover the sickest Americans if the healthiest ones are not required to pay for coverage. If the pool of the insured was composed disproportionately of the sick, insurance costs could soar.


But the White House says an array of other provisions in the law could stand. They include a vast expansion of Medicaid and the establishment of health insurance exchanges, offering subsidized coverage to those with low incomes, both scheduled to start in 2014.


Mr. Clement, representing the opponents, said the mandate was its keystone and that the entire enterprise must collapse without it.


“If the individual mandate is unconstitutional,” he said, “then the rest of the act cannot stand.”


Last year, the United States Court of Appeals for the 11th Circuit, in Atlanta, ruled that the mandate was unconstitutional, but it said the balance of the law survived.


Neither side agreed with the appeals court’s analysis of whether the mandate could be surgically removed, or severed, without doing damage to at least parts of the rest of the law.


On Thursday, Mr. Farr defended the appeal’s court ruling on severability. He said the law minus the mandate would be less desirable and effective but that the task of addressing that should fall to Congress.


One practical question is whether Congress, deeply divided along partisan lines, would be able to pass new health care laws anytime soon.


Justice Kennedy referred to this, asking if the job of reworking health care would fall “the real Congress or a hypothetical Congress.”