NEW YORK (Reuters) — Wal-Mart Stores Inc. said it plans to seek a reversal of Tuesday’s decision by a federal appeals court to approve class-action status for women who claim the retailer was biased in pay and promotion.

Earlier in the day, the largest sexual discrimination lawsuit in U.S. history moved forward against Wal-Mart (Charts) when a federal appeals court approved class-action status for seven women who claim the retailer was biased in pay and promotions.

The plaintiffs estimate as many as 1.6 million women who have worked for Wal-Mart in its U.S. stores since 1998 could join the lawsuit. The number makes the group the largest ever to sue for gender discrimination.

“We hold that the district court acted within its broad discretion in concluding that it would be better to handle this case as a class action instead of clogging the federal courts with innumerable individual suits,” Judge Harry Pregerson wrote for the United States Court of Appeals for the Ninth Circuit.

“Although the size of this class action is large, mere size does not render the case unmanageable,” he said.

In the Wal-Mart case, the plaintiffs allege they were denied promotion opportunities, with some also saying they were sexually harassed or subject to sexist remarks.

The 2-1 ruling by the three-judge panel took no position on those claims, stressing the decision only affirmed a lower court ruling to certify the case, Dukes v. Wal-Mart, as a class action against the world’s largest retailer.

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