U.S. importers are concerned a two-day strike at the East Coast's largest ocean freight terminals is a harbinger of growing militancy following 30 years of labor peace along the region's docks. The Sept 28-29 shutdown of the Port of New York-New Jersey by the International Longshoremen's Association halted an estimated 10,000 to 11,000 truck moves and caught the attention of the nation's largest retailers at the busiest time of their year. In the past, historically problematic West Coast labor relations pushed many shippers to diversify supply chains, bringing more goods east, but ILA changes and an increase in labor unrest threaten to upset their systems once again.