SAN FRANCISCO -- Cargo ships lay at anchor offshore, waiting to be unloaded, and trucks with fresh produce lined up outside West Coast ports Monday after dockworkers were locked out in a dispute that could cost the U.S. economy $1 billion a day.

West Coast shipping lines said they will keep the ports closed until the longshoremen agree to extend their expired contract. But the 10,500-member union said it will not budge until the lockout is ended.

The Bush administration said that it is concerned about the effect on the struggling U.S. economy but that it has no immediate plans to break the impasse by declaring a national emergency.

The U.S. economy would lose $4.7 billion in wages and revenue during a five-day shutdown, according to a study conducted for the Pacific Maritime Association, which represents shipping lines and sea terminal operators. A 10-day shutdown could cost $19.4 billion as economic problems snowball.

"It's just massive," said John Martin, president of Martin Associates, the Lancaster, Pa., economic consulting firm that conducted the study.

The bulk of the nation's imports from China and Japan come through the ports of Long Beach and Los Angeles, the nation's busiest. The labor crisis comes as importers scramble to bring in merchandise for the Christmas shopping season.

Representatives of the shipping lines and dockworkers met Monday afternoon but reported no major progress in the talks. Union officials said both sides planned to meet with a federal mediator Tuesday. The maritime association offered no immediate confirmation that such a meeting would take place.

A frail labor peace between the shipping lines and the longshoremen collapsed Sunday when the dockworkers were ordered off their jobs indefinitely at all 29 of the nation's major West Coast ports.

The two sides are at odds over pensions and other benefits, as well as cargo-handling technology that the union fears would wipe out jobs.

West Coast ports handled more than $300 billion in cargo over the past year. Major imports include industrial machinery, furniture, clothing, toys, computers, automotive goods and electronics. The biggest imports include meat and poultry, industrial equipment, animal feed, automotive parts, chemicals and fruit and vegetables.