A sex discrimination lawsuit against Wal-Mart cannot move forward as a class action, the U.S. Supreme Court ruled Monday.

The lawsuit against the world's biggest retailer was filed in 2001 by six women who claimed the company had discriminated against them in training, promotions and pay.

The 9th U.S. Circuit Court of Appeals in San Francisco later ruled that the case could proceed as a class action and said potential plaintiffs include all of the roughly 1.6 million "women employed in any Wal-Mart store in the United States from December 1998 on."

In a 5-4 decision, the Supreme Court said that there could not be a class action suit in this case, something along the lines of what Wal-Mart had argued.

"We are pleased with today's ruling and believe the court made the right decision. Wal-Mart has had strong policies against discrimination for many years," Executive Vice President Gisel Ruiz said on behalf of the Arkansas-based giant.

The high court ruled that the plaintiffs' attorneys had not proven that a general policy existed at Wal-Mart to discriminate on the basis of sex.

The complaint, if it would have been accepted as a class action, could have led to billions of dollars in compensation and indemnities.

Writing for the majority, Justice Antonin Scalia said that the plaintiffs did not have enough reasons in common to allow their separate complaints to be grouped into a single class action suit.

Justice Ruth Bader Ginsburg, however, wrote in her dissent that "Wal-Mart's delegation of discretion over pay and promotions is a policy uniform throughout all stores."

Justices Stephen Breyer, Sonia Sotomayor and Elena Kagan also dissented.

The ruling boosted the price of Wal-Mart shares on the New York Stock Exchange.

The case had been one of the most significant labor relations disputes in recent memory, partly because the Supreme Court magistrates had not agreed to hear such a class determination case in more than a decade.

More than 20 companies expressed before the high court their support for Wal-Mart's position, including Intel, Altria Group, Bank of America, Microsoft and General Electric.

The plaintiffs has alleged that the rejection of the class action suit would leave every woman with the sole option of initiating an individual lawsuit against Wal-Mart, something that would be virtually impossible given the costs and legal resources needed for those cases.

Betty Dukes, a greeter at a Wal-Mart in Pittsburg, California, sued the company in 2001, claiming that because she was a black woman the firm had discriminated against her both in terms of her pay and her chances for promotion.

Five other women soon joined the suit and the 9th Circuit eventually certified Wal-Mart's female employees as a class.

The company, however, said there was no basis for a class action because the hundreds of thousands of women involved "had different jobs, in different stores, in different states and under the supervision of different managers."

Wal-Mart, with annual sales of $400 billion and profits of more than $15 billion over the past 12 months, has 3,400 stores in the United States and 170 different categories of employees.