The loading and unloading of freighters will be suspended at all 29 U.S. West Coast ports this weekend, shipping companies said on Friday, citing chronic cargo backups that the shippers and dockworkers union have blamed on each other during months of labor tensions. But terminal yard, rail and gate operations at the ports, handling nearly half of U.S. maritime trade and over 70 percent of imports from Asia, will go on at the discretion of terminal managers through Saturday and Sunday, the Pacific Maritime Association said. The announcement added to the discord surrounding negotiations of a new labor contract for 20,000 dockworkers, represented by the International Longshore and Warehouse Union, that have dragged on for nearly nine months. “In light of ongoing union slowdowns up and down the coast which have brought the ports almost to a standstill, PMA member companies finally have concluded that they will no longer continue to pay workers premium pay for diminished productivity,” the association said in a brief statement. It said vessel loading and unloading operations were scheduled to resume on Monday, while yard operations - moving unloaded cargo containers for truck and rail delivery to customers - would continue at terminal operators’ discretion. The union, insisting the parties were near a settlement in the federally mediated talks, branded the shippers’ move another act of public posturing that distracted from negotiations. Two days earlier, the PMA’s chief executive, James McKenna, warned that ports plagued by worsening cargo congestion were nearing the point of complete gridlock. The companies have repeatedly accused the union of orchestrating work slowdowns to gain leverage in negotiations that have dragged on for nine months The union denies this and has faulted the carriers for the congestion, citing numerous changes in shipping practices as contributing factors. “Closing down the ports over the weekend is a crazy way to do business because it’s hurting customers and adding to the already serious congestion crisis that the industry has created,” union spokesman Craig Merrilees said. “We can’t afford to be distracted by gimmicks and games.” Crippling backups that began at the ports in October have rippled through the U.S. commercial supply chain, disrupting shipments of a wide range of goods affecting agriculture, manufacturing, transportation and retail. The congestion has been most pronounced at the ports of Los Angeles and Long Beach, the nation’s two busiest cargo container hubs, where more than 20 freighters have been left idled at anchor each of the past few days, waiting for berths to open. The National Retail Federation urged the parties on Friday to cease the “escalating rhetoric, the threats, the dueling press releases” in order to find common ground. The last time dockworkers’ contract negotiations led to a full shutdown of the West Coast ports was in 2002, when the companies imposed a lockout that was lifted 10 days later under a court order sought by President George W. Bush. Then as now, the companies accused the unions of instigating work slowdowns, and the union blamed management. The PMA has estimated that the 2002 lockout caused $15.6 billion in economic losses. When it ended, some 200 freighters were waiting at anchor to be unloaded.