Dockworkers and their employers agreed to extend contract negotiations for an additional 30 days after coming to an agreement on container royalties, avoiding a strike that would have shut down 15 East Coast and Southeast ports from Maine to Texas when the contract expired at midnight on Dec. 30.

According to the federal mediator who has been working with The International Longshoremens Association and United States Maritime Alliance, the sticking point of container royalty payments has been agreed upon in principle by both parties. These royalties supplement the wages of the longshoremen.

The details of that agreement are not being released, since negotiations are continuing. The extra 30 days is designed to give them time to negotiate the rest of the issues.

"While some significant issues remain in contention, I am cautiously optimistic that they can be resolved in the upcoming 30-day extension period," said Federal Mediation & Conciliation Service Director George Cohen in a statement.

If a strike had occurred, workers wouldnt have moved containerized cargo. Passenger ships, military cargo, containerized mail, bulk items, finished autos and perishable items with a limited shelf life would still have been handled. More than half of the nations containerized shipments pass through East Coast and Gulf Coast ports, according to Bloomberg.

Retailers welcomed the news, but continue to urge both parties to keep working on a long-term contract agreement.

While a contract extension does not provide the level of certainty that retailers and other industries were looking for, it is a much better result than an East and Gulf Coast port strike that would have shut down 14 container ports from Maine to Texas," said National Retail Federation President and CEO Matthew Shay in a statement.

A coast-wide port shutdown is not an option. It would have severe economic ramifications for the local, national and even global economies and wreak havoc on the supply chain."