Los Angeles ? The dock shutdown on the West Coast tightened the squeeze on businesses across the country Tuesday, holding up Christmas toys and worrying automakers that rely on just-in-time delivery of parts.

The lockout of dockworkers at all 29 West Coast ports is also hurting freight railroads and trucking companies that haul cargo to and from the coast. Some businesses are considering sending goods by air, a more expensive option.

If the labor dispute is not settled quickly, business leaders said, shoppers could see higher prices and less selection this holiday season.

“This is the two-minute warning for the Christmas season. We got hit at the most vulnerable moment,” said Charlie Woo, founder and chief executive of Megatoys in Los Angeles, which has $750,000 worth of toys in transit. “The customer wants my stuff, but it’s on the water.”

The Pacific Maritime Assn., which represents shipping companies and terminal operators, has locked out about 10,500 members of the International Longshore and Warehouse Union since Sunday.

On Tuesday, a federal mediation session fell apart before it began. Union representatives stormed out, saying their employers showed up with “gun-toting security guards.”

Jim Spinosa, the union’s president and chief negotiator, accused the Pacific Maritime Assn. of sabotaging the session. “PMA’s lockout is holding a gun to the head of the American economy and now they move to aim real guns at us,” Spinosa said.

A spokesman for the association said the guards were there to ensure the safety of the association’s president and chief negotiator.

“They have been deployed in a very discreet manner, and we would hope the union would understand these circumstances,” spokesman Steve Sugerman said.