The National Retail Federation has asked the White House to force striking clerical workers at Southern California ports to return to the bargaining table. About 800 members of a unit of the International Longshore and Warehouse Union went on strike Tuesday at the largest terminal at the Port of Los Angeles and the strike spread Wednesday to 10 of the 14 cargo terminals at the ports of Los Angeles and Long Beach, Calif. Union truckers and longshore dock workers are refusing to cross the picket line. The union says management is shifting work away from its members to workers in other countries who are paid lower ages. Cargo terminal officials say no jobs are being outsourced and accuse the union of promoting featherbedding -- bringing in temporary workers unnecessarily. The clerks\' strike affects 600,000 other workers and is causing an estimated economic disruption of $1 billion per day, the Los Angeles Times reported. \"An extended strike this time could have a greater impact considering the fragile state of the U.S. economy,\" NRF Chief Executive Officer Matthew Shay wrote in a letter to President Barack Obama. \"The two sides must remain at the negotiating table until a deal is reached.\" No talks have been held since Monday. Paul Bingham, an economist with consulting firm CDM Smith, told the newspaper a long strike threatens to cause extensive damage to the economy. \"Retailers will have stock outages, lost sales for products not delivered,\" he said. \"There will be shutdowns in factories, in manufacturing when they run out of parts.\" Ray Ortiz Jr., a member of the ILWU Coast Committee said the union believes \"it\'s in the long-term interest of the Los Angeles-Long Beach harbor area to retain these good local jobs.\" Negotiator Stephen Berry, representing port managers, told a news conference the striking clerical workers are \"irresponsible\" and said management has offered a contract that provides \"absolute job security,\" and an average annual salary of $195,000.