IMPORT volumes through US major container ports is expected to increase 6.1 per cent in April, according to the monthly Global Port Tracker from the National Retail Federation (NRF) and Hackett Associates.

"There is positive news with both the rebound in US retail sales in February and the new filings for jobless benefits hitting a fresh three-month low last week, suggesting that the economy is gaining momentum," Hackett Associates founder Ben Hackett said.

Said NRF vice president Jonathan Gold: "With winter over, retailers are stocking up in anticipation of a busy spring and summer. So retailers are keeping a close eye on the labour situation at west coast ports to ensure that cargo continues to move smoothly."

Mr Gold noted the current contract for west coast dockers expires on June 30 but negotiations are not expected to begin until mid-May. "Companies are already exploring contingency plans in case of a disruption," he said.

Ports followed by Global Port Tracker handled 1.26 million TEU in February, the latest month for which after-the-fact numbers are available. February is historically the slowest month of the year, and the number was down 8.4 per cent from January and 1.4 per cent from February 2013.

March was estimated at 1.31 million TEU, up 15 per cent from the same month last year. April is forecast at 1.38 million TEU, up 6.1 per cent from last year; May at 1.44 million TEU, up 3.8 per cent; June at 1.43 million TEU, up 5.5 per cent; July at 1.49 million TEU, up 3.1 per cent, and August at 1.51 million TEU, up 1.2 per cent. The first half of the year is expected to total 8.2 million TEU, up 5.5 per cent over last year.

The total for 2013 was 16.2 million TEU, up 2.3 per cent from 2012's 15.8 million TEU.

Global Port Tracker, which is produced for NRF by the consulting firm Hackett Associates, covers Los Angeles/Long Beach, Oakland, Seattle, Tacoma, New York/New Jersey, Hampton Roads, Charleston, Savannah, Port Everglades, Miami and Houston on the Gulf Coast.