WASHINGTON • America may have invented slot machines and Las Vegas is a gambling haven, but one form of wagering still remains largely off-limits - unless the Supreme Court backs New Jersey's bid to legalise sports betting in a closely watched case.

The nation's top court on Monday began considering whether a ban on sports wagering in 46 of the 50 states is constitutional, a ruling which could potentially legalise a business worth tens of billions of dollars annually.

Theodore Olson, the lawyer for Governor Chris Christie and his state of New Jersey, which is challenging the ban, argued "there is illegal gambling going on" all over the state, which "can't regulate that activity" as things stand.

Opposing Christie and supporting the ban are the four major professional US sports organisations, the National Football League, the National Basketball Association, Major League Baseball and the National Hockey League.

Christie was in the courtroom to hear the opening arguments.

His state has spent years and millions of dollars waging court battles after New Jersey voters approved sports betting in a 2011 referendum.

Under a 1992 law, betting on university or professional sports is forbidden except in four states where it already existed: Nevada, Delaware, Montana and Oregon.

Horse and dog racing were also excluded from the ban.

Congress adopted the law in the belief that sports betting would threaten the integrity of athletic activity.

According to the American Gaming Association, the underground sports betting market is worth US$150 billion (S$201 billion) a year. It is a figure that appeals to 18 other states backing the challenge in hopes of getting tax and licensing revenue.

AGENCE FRANCE-PRESSE