WASHINGTON, D.C. — The new rule forcing carriers to provide details of the contents of sea containers headed for U.S. ports 24 hours before they are loaded at foreign ports go into effect Feb. 1.

The U.S. Customs Commissioner, Robert Bonner, says enforcement of the rule will start Feb. 2. The rule is another homeland security measure, aimed at preventing terrorists from shipping nuclear and other deadly weapons by sea to the U.S.

Bonner says carriers that don’t provide advance manifest information could be barred from unloading containers at a U.S. port, and also fined.

Precise information demanded by U.S. Customs under the new rule includes an exact description of container contents, the date of scheduled arrival in the U.S., the foreign port the cargo is coming from, the shipper’s name, and the name and number of the vessel carrying the cargo.

The president of Seattle, Wash., transloader MacMillan-Piper Inc. told the Puget Sound Business Journal that the new cargo container rule is a real “hot potato” for importers.

He says the rule “could hold up cargo significantly, depending on what happens over there and how stringent they’re going to be.”