The president was clearly primed to answer on Monday when asked about the law's future. His comments were his first since last week's three days of court arguments. The law was questioned by the court's five conservative members during those hearings, sometimes in bitingly critical terms. The four liberal justices seemed likely to vote to uphold it.

The law is the signature domestic achievement of Obama's term and already a prominent source of debate in the presidential campaign. The Supreme Court will decide whether to strike down part or all of the law, including its centerpiece, the requirement that nearly all Americans carry insurance or pay a penalty.

On that point, Obama seemed to send a message directly to the justices.

"I think the American people understand — and I think the justices should understand — that in the absence of an individual mandate, you cannot have a mechanism to ensure that people with pre-existing conditions get health care," Obama said.

"So there's not only an economic element to this and a legal element to this, but there's a human element to this. I hope that's not forgotten in this political debate."

Obama also made a broader case against his conservative Republican antagonists by challenging them on a matter dear to them: stopping overreach by the courts.

"For years what we've heard is the biggest problem on the bench was judicial activism or a lack of judicial restraint — that an unelected group of people would somehow overturn a duly constituted and passed law," Obama said.

He said overturning the health care law would just such an example, "and I'm pretty confident that this court will recognize that and not take that step."

Obama declined to answer what contingencies his administration might have in mind if the court does overturn the law.

The president used most of his comments to explain the ways he believes the law is helping people, including young adults who are now allowed to stay longer on their parents' health insurance, or seniors who are paying less for prescriptions. He said that doesn't count the 30 million who ultimately stand to gain coverage they now lack.

In the court arguments, the administration faced skepticism from conservative justices, heightening speculation that the law could be overturned at least in part. Those justices raised questions about Congress' power to force people to buy health insurance, a key part of the new law, suggesting problems for the insurance requirement and possibly the entire measure.

The White House has cautioned anyone against drawing conclusions from the justices' lines of questioning.

Obama said flatly he is confident the court will uphold the law: "The reason is because, in accordance with precedent out there, it's constitutional."

Obama is a graduate of Harvard Law School, and before entering politics he taught constitutional law at the University of Chicago Law School.