A federal mediator was in San Francisco Tuesday to join talks aimed at ending a labor dispute that has shut down 29 U.S. West Coast ports from Seattle to San Diego. Shipping lines locked out dockworkers after an alleged union slowdown amid stalled talks on a new contract. The shipping lines want the dock workers to resume work under a contract that expired last month, while talks on a new pact continue. The union representing more than 10,000 dock workers has refused. At the White House Tuesday, U.S. president George W. Bush said he was concerned about the economic impact of the shutdown. Some economists say the dispute could cost the sluggish U.S. economy more than one-billion-dollars-a-day.

?We're watching it very closely. A federal mediator is on the ground and I urge both parties to utilize the mediator. But we'll continue to pay attention to it, it's a problem. It's something we just going to have to get these parties to work through and get back to work and open these ports up. It's important to our economy to do so."

As much as 40 percent of America?s trade is conducted through West Coast ports. Further delays in shipping goods could hurt U.S. consumers and may cause plant lay-offs in many industries. Negotiations on a new contract are deadlocked on several issues, including a computerized system that could reduce the number of dock jobs, as well as pensions and benefits. President Bush could declare a national emergency and order the ports reopened, but the White House has given no indication that Mr. Bush may do so.