LOS ANGELES -- A strike at the ports of Los Angeles and Long Beach is entering its fourth day despite efforts to end a walkout that's largely idled the nation's busiest cargo complex.

Port officials say seven out of eight LA terminals and three of six in Long Beach are closed to container traffic Friday as dockworkers refuse to cross picket lines set up by union clerical workers.

At least 18 cargo ships haven't been serviced since workers struck Tuesday. Los Angeles port spokesman Phillip Sanfield says a handful of vessels that were anchored offshore have left for other ports.

The clerical workers claim that shippers are outsourcing their well-paid jobs overseas. The shippers deny it.

Contract talks resumed Thursday and will continue Friday.