San Francisco ? Cargo ships lay at anchor offshore, waiting to be unloaded, and trucks with fresh produce lined up Monday outside West Coast ports 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 would keep the ports closed until the longshoremen agree to extend their expired contract. But the 10,500-member union said it would not budge until the lockout is ended.

The Bush administration said it was concerned about the effect on the struggling U.S. economy but that it had 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 Assn., 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 today with a federal mediator. The maritime association offered no immediate confirmation that such a meeting would take place.

A frail labor peace collapsed Sunday when 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 in the past year. Major imports include industrial machinery, furniture, clothing, toys, computers, automotive goods and electronics. The biggest exports include meat and poultry, industrial equipment, animal feed, automotive parts, chemicals, and fruit and vegetables.

Dozens of ships waiting to be unloaded dropped anchor outside the ports in cities including Los Angeles, Oakland, Seattle and Tacoma, Wash., according to the maritime association including 46 in Southern California ports alone. Seventy other vessels already in port waited to be loaded or unloaded.

West Coast shipping lines say they will keep ports closed until the longshoremen agree to extend their expired contract. But the 10,500-member dockworkers union said it would not budge until the lockout ends. On Monday, longshoreman Aaron Hardin, above, was among the locked-out employees who picketed outside the gates at the Port of Oakland.

Economists warned that a drawn-out work stoppage will ripple through the U.S. economy. Stores will not have the merchandise they need. Produce could rot on the docks. Assembly lines may come to a halt for lack of parts.

Hawaii alone relies on shipping for about 90 percent of its goods.

At New United Motor Manufacturing Inc., in Fremont, Calif., officials said they would have to shut down production by week’s end if motors and transmissions in containers at the Port of Oakland don’t arrive on time.

“You simply cannot find an alternative for parts,” said NUMMI spokesman Michael Damer.

For truckers such as Salvador Nunez, the effect was more immediate. He drove to the Port of Los Angeles from a small town near the Mexican border with a load of alfalfa sprouts and hay. Unable to unload, he waited several hours before turning around for the six-hour ride home.

Nunez was out $125 in transportation costs and could not collect his usual $400 for the load. If the work stoppage goes on for more than a week, “it will be too long,” said Nunez, who supports a wife and two children. “I’ll be out of money.”

Maritime association president Joseph Miniace ordered the lockout Sunday and accused the union of disrupting work by understaffing operations and dispatching workers not skilled for specific jobs. He demanded the dockworkers agree to extend their contract.

Jim Spinosa, president and chief negotiator for the International Longshore and Warehouse Union, said: “The ILWU will not be intimidated. We will not extend the contract.”

The last time an economic emergency was declared and the government intervened in a work stoppage under the Taft-Hartley Act was 1978, when President Carter unsuccessfully tried to end a national coal strike. No such action is planned yet by the Bush administration.

“If it goes on for even a short period of time, it’s a problem for the economy,” White House spokesman Ari Fleischer said. “We’re monitoring it closely.”

Under the last contract, a full-time longshoreman makes an average of $80,000 a year, while the most experienced foremen average $167,000.

The talks began deteriorating during the summer, and over Labor Day weekend the union stopped approving rolling extensions of the contract, which officially ended July 1.