The nation's major retail container ports can expect double-digit increases in import cargo volume in the months ahead, according to the monthly Global Port Tracker report

released by the National Retail Federation and Hackett Associates. The report said container traffic is expected to gain 15 percent in June from the year-ago month.

"Cargo import numbers are up but retailers are looking closely at other economic indicators to make sure they are sourcing the appropriate amount of merchandise based on consumer demand," said Jonathan Gold, NRF vice president for supply chain and customs policy. "Job creation remains a key factor that's going to affect consumer spending and retail sales."

U.S. ports handled 1.15 million Twenty-foot Equivalent Units, or TEUs in April, 7 percent higher than March and 16 percent above April 2009. It was also the fifth month in a row to show a year-over-year improvement after December broke a 28-month streak of year-over-year monthly declines.

May was estimated at 1.16 million TEUs, a 12 percent boost over last year as spring products hit store shelves and summer merchandise followed close behind. June is forecast to stay at 1.16 million TEUs, but the figure would be up 15 percent from last year. July is forecast at 1.23 million TEUs, up 11 percent from last year; August at 1.27 million TEUs, up 10 percent; September at 1.31 million TEUs, up 15 percent. October, which is typically the busiest month of the year, should be at 1.34 million TEUs, up 12 percent.

The first half of 2010 is expected to total 6.6 million TEUs, a 12 percent increase from the same period last year. Imports for 2009 totaled 12.7 million TEUs, down 17 percent from 2008 and the lowest since the 12.5 million TEUs reported in 2003.