Imports at 10 top U.S. container gateways are expected to increase nearly 10 percent in October as merchants wrap up their pre-holiday shipping season, the National Retail Federation and Hackett Associates said in their monthly Global Port Tracker report.

Containerized imports through the ports are expected to total 1.45 million 20-foot-equivalent units in October, a 9.9 percent increase from a year earlier, the forecast said. September was estimated at 1.49 million, up 8 percent.

The estimates were little changed from last month’s Port Tracker, which forecast 1.48 million TEUs in October and 1.45 million in September.

There had been speculation that October volumes could be affected by early shipments to avoid a threatened International Longshoremen’s Association strike on Sept. 30. The ILA and East and Gulf coast employers have extended their contract through Dec. 29.

The latest Port Tracker, however, showed little change from last month’s forecasts. “Inventories are up, which could be due to lack of demand but it could also be due to pre-stocking in anticipation of the dock strike that didn’t come,” said Ben Hackett, founder of Hackett Associates. “Either way, it is within a narrow range of movement and it does not suggest that we are sliding into another recession.”

Jonathan Gold, the NRF’s vice president for supply chain and customs policy, said import volumes are based on prospects for healthy holiday sales. “NRF’s annual forecast says retailers should see solid growth during the holiday season this year and these cargo numbers back it up,” he said. “Increased imports show that retailers have gauged the market and expect increased sales.”

Volume for August, September and October, the traditional peak season for imports, were up 7 percent year-over-year. Although cargo volume doesn’t correlate directly with sales, the NRF forecast last week that holiday sales would increase 4.1 percent to $586.1 billion this year.

U.S. ports followed by Global Port Tracker handled 1.42 million TEUs in August, the latest month for which after-the-fact numbers are available. That was up 6.7 percent from July and 3.3 percent from August 2011.

With most holiday merchandise already at least in distribution centers by the end of October, monthly cargo volume will drop off for the remainder of the year but will remain above 2011 levels, the report said.

November is forecast at 1.32 million TEUs, up 2.4 percent from last year and unchanged from last month’s Port Tracker forecast. December is forecast at 1.28 million TEUs, up 4.6 percent from a year earlier and slightly above the 1.25 million forecast last month. The January 2013 forecast is 1.28 million TEUs, down 0.5 percent from January 2012, and above the 1.23 million forecast last month. February is forecast at 1.19 million TEU, up 9 percent from a year earlier.

The first half of 2012 totaled 7.7 million TEUs, up 2.9 percent from the same period last year. For the full year, 2012 is expected to total 16 million TEUs, up 4.1 percent from 2011.

Import gateways covered by the report are Los Angeles-Long Beach, Oakland, Seattle and Tacoma on the West Coast; New York-New Jersey, Virginia, Charleston, Savannah, Port Everglades-Miami on the East Coast, and Houston on the Gulf Coast.