The union representing 14,500 dockworkers in East and Gulf Coasts ports, including Philadelphia, and management for shipping lines and port employers are lurching toward a possible crippling strike next week.

Negotiations between the International Longshoremen's Association (ILA) and employers represented by the U.S. Marine Alliance broke off Tuesday.

If the stalemate is not resolved, workers between Maine and Texas could walk off the job Dec. 30.

The bargaining is for a new master contract governing containerized cargoes - commodities shipped in 20- or 40-foot containers.

Ports on the Delaware would not be as severely disrupted as some ports, such as New York, because more cargoes arrive here in bulk or smaller crates, and on pallets, including plywood, steel, paper, cocoa beans, and fruit.

Longshoremen who handle cargoes not shipped in containers would stay on the job in the event of a strike.

The Packer Avenue Marine Terminal in South Philadelphia would be the operation most disrupted locally. About half of the cargoes at Packer are in containers, said Tom Holt Jr., who runs the terminal.

"The ports are preparing contingency plans," Holt said. "We'll be working with our customers between now and when the contract expires on the 29th to get as much cargo in and out. We're going to extend our gate times, to get traffic on and off the port, and accommodate our customers' needs."

Robert Palaima, president of the Delaware River Stevedores, said the Tioga Marine Terminal in Port Richmond would "hopefully be unaffected by a labor action."

"We are saying to our customers that if the ILA provides us with labor, we are going to go to work," Palaima said. "Nonetheless, everyone is still nervous, because you come into these strike situations and confusion abounds."

Stuart Jablon, Dole Fresh Fruit Co. vice president for operations in Wilmington, said he was confident the ILA would not strike Dole and Chiquita's perishable cargo operation.

"They know that Dole and Chiquita have supported the ILA since its inception," Jablon said. "We use ILA labor in all the ports in North America."

A strike was averted Oct. 1 when both sides agreed to a 90-day extension through Dec. 29 - after the U.S. elections and the holiday shopping season.

The National Retail Federation said a strike or lockout - on the heels of Hurricane Sandy, which closed the Port of New York and New Jersey, and a recent eight-day strike by harbor clerks in Los Angeles and Long Beach, Calif. - would be a huge blow to importers and exporters.

A Maine-to-Texas longshoremen's strike, called a coast-wide strike, would disrupt retailers' shipments of spring and summer merchandise, such as Easter shoes, home goods, swimwear, and patio furniture, and affect manufacturers, wholesalers, truck drivers, and farmers, the trade group said.

A major strike would affect thousands of jobs and cost the economy millions of dollars a day.

The federation urged President Obama to intervene and both sides to stay at the table until a deal is reached.

The last coast-wide longshoremen's strike was in 1977.

Talks broke off Tuesday over the issue of "container royalties," payments made to longshoremen based on the weight of containerized cargo. Management wants to cap those payments.

The ILA said it was willing to extend the contract to Feb. 1 and keep talking, but only if management would take the container royalty cap off the table.

"They refused, so right now, unless we hear back from them, we will be on strike on Dec. 29," ILA executive vice president Benny Holland told the trade magazine American Shipper.