US authorities will send nuclear detection devices to Port Qasim, Pakistan; Puerto Cortes, Honduras; Southampton, Britain; Port Salalah, Oman; the Port of Singapore; and the Gamman Terminal at Port Busan, South Korea.
Starting in early 2007, containers at the six ports will be scanned for radiation before they are cleared for shipping to the United States, the Homeland Security and Energy departments said in a statement.
Homeland Security and host country officials will simultaneously receive an alert in the event of a detection alarm, the statement said.
"Our highest priority and greatest sense of urgency has to be aimed at preventing a nuclear weapon or dirty bomb attack against the homeland," Homeland Security Secretary Michael Chertoff said in a statement.
"This initiative advances a comprehensive strategy to secure the global supply chain and cut off any possibility of exploitation by terrorists," Chertoff said.