The US Supreme Court ruled for Walmart Stores Inc. in the largest sex-discrimination lawsuit ever, overturning a decision that gave class-action status for female employees seeking billions of dollars.

The justices on Monday overturned a US appeals court ruling that more than a million female employees nationwide could join together in the lawsuit accusing Walmart of paying women less and giving them fewer promotions.

The supreme court accepted Walmart's main argument that the female employees in different jobs at 3,400 different stores nationwide and with different supervisors do not have enough in common to be lumped together.

The court only decided whether the 10-year-old lawsuit can proceed to trial as a group in a class-action suit, not the merits of the sex-discrimination allegations at the heart of the case.

Justices divided

The justices were divided 5-4 on another aspect of the ruling that could make it much harder to mount similar class-action discrimination lawsuits against large employers.

Justice Antonin Scalia concluded for the court conservative majority that the class was not properly certified and said there must be significant proof that Wal-Mart operated under a general policy of discrimination.

"That is entirely absent here," Scalia said.

Justice Ruth Bader Ginsburg, writing for the court's four liberal justices, said there was more than enough uniting the claims. `

"Walmart's delegation of discretion over pay and promotions is a policy uniform throughout all stores," Ginsburg said.

Walmart, the world's largest retailer and the largest private US employer, has denied the allegations and said it has operated under a policy barring discrimination.

Al Jazeera's Monica Villamizar, reporting from Washington DC, said the women are probably still going to sue, however as individual cases, which will not have the same impact. 

Walmart shares rose after news of the decision, rising 46 cents, almost 1 per cent, in the morning trading on the New York Stock Exchange.

"It is a big legal victory for Walmart," our correspondent said.