Major U.S. retail container ports should see import cargo volume climb 11 percent in March, a monthly report by Global Port Tracker showed, in yet another sign that the U.S. economy is gaining strength.

The report, released by the National Retail Federation and consulting firm Hackett Associates, also forecast imports of 7.5 million Twenty-foot Equivalent Units in the first half, up 9 percent from the first half of 2010. One TEU is one 20-foot cargo container or its equivalent.

"These numbers show solid increases over last year and are evidence that our nation's economic recovery is continuing to build momentum," NRF Vice President for Supply Chain and Customs Policy Jonathan Gold said.

"Increases in imports are a clear sign that retailers expect sales to continue to climb in the next several months."

U.S. ports followed by Global Port Tracker handled 1.2 million Twenty-foot Equivalent Units in January, the latest month for which numbers are available. That was up 5 percent from December and up 12 percent from January 2010.

Imports in February, traditionally the slowest month of the year, were estimated at 1.12 million TEU, which would be a 12 percent rise from a year earlier.

Global Port Tracker covers the U.S. ports of Long Angeles/Long Beach, Oakland, Seattle and Tacoma on the West Coast; New York/New Jersey, Hampton Roads, Charleston and Savannah on the East Coast, and Houston on the Gulf Coast. (Reuters)