Container ships have begun diverting to other ports in California and Mexico as a strike continues to disrupt docking facilities in Los Angeles, a key gateway for trade with Asia, according to an official. As a trade group urged President Barack Obama to intervene, Port of Los Angeles head Geraldine Knatz also warned that the three-day-old strike could damage the US economy and harm the reputation of the key shipping hub. \"This dispute has impacted not only our port workforce but all stakeholders who ship goods through our complex and potentially the hundreds of thousands of jobs that are directly and indirectly related to port operations,\" she said. \"In today\'s shipping environment, we can\'t afford to lose cargo or our competitive advantage,\" she added Thursday, saying ships were diverting notably to Oakland, up the coast near San Francisco, and to Mexico to the south. The action by clerical staff started at a terminal in the port of Los Angeles on Tuesday but spread to six other terminals and the nearby port of Long Beach on Wednesday. No progress was reported in negotiations Thursday. The two ports deal in $1 billion of cargo per day on average, a huge proportion of it shipments to and from Pacific nations. The striking workers claim that the Harbor Employers Association wants to outsource jobs, but employers\' spokesman Stephen Berry said the strike was over \"demands that we hire people they don\'t need.\" He added that clerks get eleven weeks holiday per year and have an absenteeism rate of 29 percent. Meanwhile, the National Retail Federation (NRF) called for the White House to help unblock the negotiations. \"A prolonged strike at the nation\'s largest ports would have a devastating impact on the US economy,\" NRF head Matthew Shay wrote in a letter to Obama. \"We call upon you to use all means necessary to get the two sides back to the negotiating table.\" The port in Los Angeles and the one in neighboring Long Beach constitute the seventh busiest commercial harbor in the world, handling more than 40 percent of ocean-shipped US imports from Asia.