A potential labor strike by longshoremen along the U.S. East and Gulf Coasts at the end of the year could have devastating economic consequences as inventory depletion, rerouting, hoarding, and price speculation ripple through supply chains of global companies, according to a report from the Marsh research firm.

Import cargo volume at the nation's major retail container ports is expected to increase 3.9 percent in December despite a strike that closed the nation's largest port complex for the first few days of the month, but retailers are keeping a close watch on a possible strike on the East Coast and Gulf Coast, according to the monthly Global Port Tracker report released today by the National Retail Federation and Hackett Associates.