Movement of shipping containers filled with goods meant for sale prior to the December holidays is being slowed by jams at overloaded ports and trucking terminals.

The New York Times reported that U.S. retailers are waiting longer than usual – several weeks in some cases – for Asian-made goods that arrive by ship, rail and truck.

The reported cause of the delays is the growth in imports from countries like China and India, a lack of dockworkers to unload containers and a shortage of truckers to move such goods cross-country by highway. Rail lines are also overloaded, The Times reported.

“It is certainly going to impact retailers as they get ready for the Christmas rush,” said Peter H. Powell, chairman of the National Customs Brokers and Forwarders Association of America.