The impasse in negotiations over a new labour agreement for US west coast dockers is starting to disrupt the flow of goods in and out of the United States, the port employers’ organisation has warned.

The Pacific Maritime Association said in a statement issued on Friday that members of the International Longshore and Warehouse Union had unilaterally changed working practices at the twin ports of Los Angeles and Long Beach, making them less efficient. The two ports - the busiest two container ports in the US - together handle around 40 per cent of US container traffic.