WASHINGTON - After a day of preliminary arguments on the 2010 health care overhaul that was short on rhetorical fireworks, the justices of the U.S. Supreme Court will reconvene Tuesday to hear testimony on the law's requirement that most Americans get health insurance.

The so-called individual mandate is the most contested provision of the Affordable Care Act and presents the court with a critical question about the constitutional limits of Congress's authority: Can lawmakers revamp the nation's health care system so that a vast majority of Americans are covered by insurance?

Two hours have been set aside Tuesday for oral arguments on the mandate, the biggest chunk of time for any of the four issues facing the court as it considers the health care law this week.

Solicitor General Donald Verrilli, the Supreme Court lawyer for President Barack Obama's administration, will tell the court the individual mandate is well within Congress's authority to regulate interstate commerce, as everyone will have to use health care services at some point in life.

Paul Clement, representing 26 states that are challenging the law, will counter that the mandate is an unprecedented overreach by the government to force Americans to buy a private product or be penalized.

Also challenging the law will be Michael Carvin of the firm Jones Day, who is representing the National Federation of Independent Business, which has sued to have the entire law struck down as unconstitutional because of the cost burden it would impose on employers.