Wal-Mart will face a class action claim by U.S. female workers, a U.S. court ruled. The women allege the retailer discriminated against them.

A sharply divided U.S. federal appeals court on Monday exposed Wal-Mart Stores Inc. to billions of dollars in legal damages when it ruled a massive class-action lawsuit alleging gender discrimination over pay for female workers can go to trial.

In its 6-5 ruling, the 9th Circuit U.S. Court of Appeals said the world's largest private employer will have to face charges that it pays women less than men for the same jobs and that female employees receive fewer promotions and have to wait longer for those promotions than male counterparts.

The retailer, based in Bentonville, Ark., has fiercely fought the lawsuit since it was first filed by six women in federal court in San Francisco in 2001, losing two previous rulings in the trial court and again in the appeals court in 2007.

Wal-Mart successfully persuaded the appeals court to revisit its 2007 ruling, made by a three-judge panel, with a larger, 11-judge panel, arguing that women who allege discrimination should file individual lawsuits.

The retailer argued that the number of litigants that the lawsuit purports to represent is too big to defend.

"Although the size of this class action is large, mere size does not render a case unmanageable," Judge Michael Daly Hawkins wrote for the majority court, which didn't address the merits of the lawsuit, leaving that for the trial court.

Judge Sandra Ikuta wrote a blistering dissent, joined by four of her colleagues.

"No court has ever certified a class like this one, until now. And with good reason," Ikuta wrote. "In this case, six women who have worked in 13 of Wal-Mart's 3,400 stores seek to represent every woman who has worked in those stores over the course of the last decade — a class estimated in 2001 to include more than 1.5 million women."

A Wal-Mart representative said the retailer was preparing a statement.

The lawsuit was filed in 2001 and includes more than one million current and former workers.