Negotiators will return to the table one more time to try and avert a "container cliff": a looming port strike that could shut down shipping on the East Coast.

The longshoreman's union and port management have until Saturday to reach a deal on a new contract. If not, the longshoreman will walk off the job December 29.

They'll be off the job in the Port of New York/New Jersey and the Delaware River port in Philadelphia.

They're negotiating with the US Maritime Alliance (USMX) with help from a federal mediator. The sticking point is the level of royalty fees - payments made to the union for each container handled to compensate longshoremen for jobs lost due to mechanization.

If the port strikes happen, they would be the biggest on the East Coast since 1977.

Last week, the National Retail Federation asked President Obama to intervene to prevent the walk-out. They argued that it would have "serious economy-wide impacts."