The backup of container ships waiting to enter the nation’s busiest port complex isn’t letting up. But it has moved farther from shore.

Only about 30 vessels sat within sight of the ports of Los Angeles and Long Beach this week, waiting for berths at a gateway that has come to symbolize U.S. supply-chain bottlenecks. More than 60 others destined for the port complex remained in waters farther out to sea, some hundreds or even thousands of miles away, including ships that reduced speed during their voyage from Asia to delay their arrival.

The ships are complying with a voluntary system set up last month by maritime officials because of fears the ports can’t safely accommodate the crush of waiting for vessels as winter weather sweeps in with strong winds and rough seas.

Before the new system was put in place, many ships rushed across the Pacific to secure a berth at a container terminal by crossing a line 20 nautical miles from the ports, said Jessica Alvarenga, a spokeswoman for the Pacific Merchant Shipping Association, which represents ocean carriers and West Coast terminal operators.