WASHINGTON (AP) The Supreme Court will consider whether to keep alive the largest job discrimination case in US history, a lawsuit against Wal-Mart that grew from a half-dozen women to a class action that could involve billions of dollars for more than a half million female workers.

Wal-Mart is trying to halt the lawsuit, with the backing of many other big companies concerned about rules for class-action cases those in which people with similar interests increase their leverage by joining in a single claim. Class actions against discount seller Costco and the tobacco industry are among pending claims that the high court’s decision might alter.

The suit against Wal-Mart Stores Inc. contends that women at Wal-Mart and Sam’s Club stores are paid less and promoted less often than men. The case the high court accepted yesterday will not examine whether the claims are true, only whether they can be tried together.

Estimates of the size of the class range from 500,000 to 1.5 million women who work or once worked for Wal-Mart.

Wal-Mart is appealing a ruling by the 9th US Circuit Court of Appeals in San Francisco that the class-action lawsuit could go to trial.

Tobacco giant Altria Corp., Bank of America Corp., Dole Food Company Inc., General Electric Co., Intel Corp., Pepsico Inc. and United Parcel Service Inc. are among the companies that also called for high court review of the case.

Wal-Mart praised yesterday’s Supreme Court intervention.

“The current confusion in class action law is harmful for everyone employers, employees, businesses of all types and sizes, and the civil justice system,” Wal-Mart said in a statement. “These are exceedingly important issues that reach far beyond this particular case.”

Lawyers representing the women said they are eager to resolve procedural issues that have delayed the trial.

They said they “welcome the US Supreme Court’s limited review of the sex discrimination case and are confident that the court will agree that the women of Wal-Mart are entitled to their day in court.”