A strike by some 24,000 refinery workers was averted, at least for now, as both sides agreed to extend negotiations for at least 24 hours.

Workers at refineries near New Orleans, Houston and as far away as Billings, Mont., will show up for scheduled shifts Monday, though negotiators will be back at the table on Sunday.

"We have made progress in that there was no strike at midnight," said Lynne Baker, a spokeswoman for the United Steelworkers, which represents more than 30,000 oil workers nationwide. "But there are still issues that need to be worked out and notice of a strike could be given at any time if that progress stalls."

The union agreed to a rolling 24-hour extension, which allows the union to give the required one-day notice to strike.

The nation's biggest refiner, Valero Energy Corp., said it would shut down some facilities if workers walk out. So did European oil company BP PLC.

Shell Oil Co., the lead negotiator for the industry, along with Exxon Mobil Corp., said its refineries would continue to make gasoline, diesel and other fuels using nonunion or replacement workers.