Crucial US health law case begins
America's Supreme Court has begun hearing arguments on President Barack Obama's controversial health care overhaul, a law that touches core political divisions.
Since Mr Obama made it law two years ago, 26 states have challenged the constitutionality of the overhaul, the largest expansion in the nation's social safety net in more than 40 years. Republicans have made repealing the law central to their bid to deny the president a second term in the November election.
All four Republicans battling for the nomination to challenge Mr Obama have promised to undo the health care overhaul, provided the conservative-dominated Supreme Court does not strike it down in a decision that is expected in June.
The fight against the law, aimed at extending health insurance to more than 30 million Americans, has further inflamed deep divisions in a country knocked off kilter by recession and embroiled in a political battle about the role of government.
Until the health care law, the United States was the only major developed country without a national health care system.
Republicans are leading the fight to kill the law either via the court or through congressional repeal. They say the worst fears about what they derisively call "Obamacare" already have come to pass in the form of higher costs and regulations, claims that the law's supporters dispute.
Polls have consistently shown the public is at best ambivalent about the benefits of the health care law and that a majority of Americans believe the insurance requirement is unconstitutional.
The hearings this week will be closely followed for clues about what the nine Supreme Court justices are thinking. The court has four liberal-leaning justices appointed by Democratic presidents - two by Mr Obama - and five conservatives appointed by Republican presidents. In order for the law to stand as written, at least one of the conservative justices will have to join the liberals in ruling to uphold the law.
The first arguments concern issues around what is known as the "mandate" that all Americans buy or have health insurance coverage.
By 2019, about 95% of the country will have health insurance if the law is allowed to take full effect, the Congressional Budget Office estimates.