IMPORT container cargo at US major ports is expected to be at some of its highest levels ever during the next few months despite a fall off from last year's record-setting numbers, according to the monthly Global Port Tracker from the National Retail Federation (NRF) and Hackett Associates.

"Retailers are importing less merchandise than last year but these are still some of the highest numbers we've ever seen," said federation vice president Jonathan Gold.

"Carefully managing imports will balance out high inventory levels but consumers can still expect to see a deep and broad selection of products," he said.

Ports covered by Global Port Tracker handled 1.32 million TEU in March, the latest month for which after-the-fact numbers are available. That was down 14.2 per cent from February, partly because of a carryover from Chinese New Year factory closings.

It was also down a dramatic 23.7 per cent from the all-time record high set in March 2015 after a new contract with dockers ended a near-shutdown at west coast ports and brought a flood of backlogged cargo through the ports.

April was estimated at 1.5 million TEU, down 0.8 per cent from the same month last year, when 2015's unusual pattern of cargo volumes started to stabilise.

May is forecast at 1.57 million TEU, down 2.7 per cent from last year; June at 1.56 million TEU, down 0.8 per cent; July at 1.61 million TEU, down 0.6 per cent; August at 1.62 million TEU, down 3.7 per cent, and September at 1.56 million TEU, down 3.9 per cent.

The 1.73 million TEU seen in March 2015 broke a previous record of 1.59 million TEU set in September 2014, and was followed by numbers as high as 1.68 million TEU before last year's unusually patterns settled down.

But this year's forecast peak of 1.62 million TEU in August would still be among the six highest months on record.

The first half of 2016 is expected to total 9 million TEU, up 1.4 per cent from the same period in 2015. Total volume for 2015 was 18.2 million TEU, up 5.4 per cent from 2014.

Hackett Associates founder Ben Hackett said the decreased imports reflect both high inventory levels and slow growth in consumer spending in recent months.

"Consumer spending is still growing but not as fast as in the past," Mr Hackett said. "A more cautious approach is being taken."

Global Port Tracker covers the US ports of Los Angeles/Long Beach, Oakland, Seattle, Tacoma, New York/New Jersey, Hampton Roads, Charleston, Savannah, Port Everglades, Miami and Houston.