A new week brings more waiting for the U.S. Supreme Court to rule on a challenge to President Barack Obama's signature health care reforms.

The high court's ruling is expected as early as Monday, which would be exactly two years after Mr. Obama signed legislation to mandate health insurance for an additional 32 million Americans and prevent coverage from being refused on the basis of patients' medical histories.

At the heart of the Patient Protection and Affordable Care Act, called “Obamacare” by its critics, lies the individual mandate. It requires every U.S. citizen to have health insurance, beginning in 2014, or be subject to a fine.

Opponents argue that Congress overstepped its constitutional authority in requiring individuals to buy insurance. The Obama administration contends the move is in line with existing law.

The nine Supreme Court justices heard six hours of oral arguments in late-March, the most time allotted to debating a single issue before the high court in more than 45 years.

There are several possible outcomes. The Supreme Court could overturn the act in its entirety, throw out only the individual mandate, endorse the entire law, or reach some other kind of ruling.

Whatever the court's decision, it will have a major impact on health care delivery in the United States, and could affect the outcome of the November presidential election.

Mr. Obama's challenger, for Massachusetts Governor Mitt Romney, says the elimination of the health care law would be the top priority in his administration's first 100 days.