Import cargo volumes at major US retail container ports are expected to rise 1.1% percent in June over the same month last year, reflecting modest growth as retailers head toward the back-to-school and holiday seasons.

The forecast from the monthly Global Port Tracker report released by the National Retail Federation (NRF) and Hackett Associates, suggests retailers are continuing to remain restrained, especially when it comes to stocking their inventories.

"With the economic recovery moving slowly, retailers are being cautious this summer and could hold off on stocking up for the holiday season until fall," said Jonathan Gold, NRF vice president for supply chain and customs policy.

"We aren't expecting significant increases for imports until October, when retailers will have a better idea of what to expect for holiday demand."

Cargo import numbers do not correlate directly with retail sales or employment because they count only the number of cargo containers brought into the country, not the value of the merchandise inside them. But the amount of merchandise imported nonetheless provides a rough barometer of retailers' expectations.

US ports followed by Global Port Tracker handled 1.31m Twenty-foot Equivalent Units (TEU) in April, the latest month for which after-the-fact numbers are available. That was up 14.6% from an unusually slow March but down 0.1% from April 2012. One TEU is one 20-foot cargo container or its equivalent.

May was estimated at 1.4m TEU, up 2.2% from a year ago. June is forecast at 1.4m TEU, up 1.1% from last year; July at 1.44m TEU, up 1.9%; August at 1.43m TEU, up 0.5%; September at 1.42m TEU, up 0.8%; and October at 1.45m TEU, up 7.9%.

The first six months of 2013 are expected to total 7.8m TEU, up 1.9% from the first half of 2012. The total for 2012 was 15.8m TEU, up 2.9% from 2011.

"We are witnessing a period of import trade growth that is running more or less in sync with the US economic expansion. Unfortunately, both are anaemic," added Hackett Associates founder Ben Hackett.

"The impact of this extremely cautious consumer spending is that we expect import consumption to remain weak for the coming four to six months."