(Illustration: Tim Lane)

The U.S. Maritime Alliance, which negotiates union contracts on behalf of shipping container terminal operators on the East coast, warned of "serious consequences for the nation’s still-recovering economy" if labor and management can't reach a new master contract by December 29.

"A shutdown would wreak havoc on manufacturers, retailers, farmers and others who depend on the ports to move their supplies and products," USMX said in a statement posted to its website.

USMX and the International Longshoremen's Association agreed to a 90-day contract extension in September that averted a possible work stoppage.

Read more: Banksters vs. Gangsters? Contract Pits Pinstriped Pinheads Against Roughneck Roustabouts.

Earlier this week, each side accused the other of scuttling a second contract extension, after the two sides failed to agree on the future of a royalty program that rewards stevedores based on the quantity of containerized cargo that crosses the docks.

"USMX seems intent on gutting a provision of our Master Contract that ILA members fought and sacrificed for years to achieve," Mr. Daggett said in a statement. "We have repeatedly asked them to leave this item alone - it was a hard won gain by ILA members and a wage supplement achieved through hard fought negotiations."

Among the consequences of a work stoppage, the USMX highlighted the effects on the New York City area as follows:

At the Port of New York and New Jersey, which employs more ILA members than any of the 13 other East and Gulf Coast ports, the union’s 3,250 members would lose $7.5 million a week in wages alone.

A strike at the port, the largest on the East Coast, could also put at risk the nearly 171,000 jobs directly related to New York and New Jersey port operations.

In New York and New Jersey, for example, a shutdown would result in $100 million in lost revenue a month for railroads, truckers and other port-related transportation industries that handle the more than 250,000 containers that move through the port each month.

In 2002, a 10-day work stoppage on the West coast container terminals is said to have cost the U.S. economy $1 billion a day.