The U.S. Supreme Court Monday announced that the justices will hear arguments on the constitutionality of President Barack Obama's health care reform law, the centerpiece of his agenda.

The justices decided to take on three legal challenges to the Affordable Care Act. They will hear five and a half hours of oral arguments. The biggest issue for the nine justices will be the constitutionality of the law's mandate that most Americans carry health insurance.

We know the Affordable Care Act is constitutional and are confident the Supreme Court will agree, the White House said in a statement following the high court's decision.

Other legal issues on Obamacare that will get attention from the justices include whether the entire law can stand if the mandate is struck down, the law's Medicaid extension is constitutional and if an obscure tax law blocks any legal challenge to the law.

The Obama administration and the group of states will get two hours to argue the constitutionality of the individual mandate. Another hour will be allotted for arguments on whether legal challenges to the Affordable Care Act can be heard.

The obscure tax law, called the Anti-Injunction Act, essentially prohibits federal courts from hearing cases challenging a tax before it is paid. This applies to health care reform because people who refuse to get health insurance will get hit with a tax penalty.

This could give the justices a way to avoid a decision on the constitutionality of the individual mandate.

Meanwhile, two Obamacare challenges -- a case from 26 state attorneys general and a small business group -- were consolidated. The justices granted the parties 90 minutes to argue whether all of the Affordable Care Act must fall if the individual mandate is severed.

The final issue for the justices will be an expansion of Medicaid. Under the Affordable Care Act, the eligibility requirements for Medicaid are expanded. States must cover these new Medicaid enrollees. Though the federal government will cover the cost of the expansion, states will start kicking in 5 percent of the costs in 2017 and 10 percent in 2020.

The justices will decide if Congress exceeded its authority in passing that provision into law.

So far, lower appellate courts have split on the constitutionality of the Affordable Care Act. A decision from the high court is expected this summer in the thick of the 2012 presidential election season.