The US Department of Homeland Security has sought more time to meet a deadline to screen all global containers bound for US ports.

The 2012 deadline to screen cargo entering the country by ship will likely be missed without investment and resources, according to US Homeland Security Secretary Janet Napolitano.

Napolitano said the department is compelled to seek time extensions authorised by law to carry out scanning procedures, according to Reuters.

According to Napolitano there remains a lack of technology to adequately screen containers, in addition to enormous expense.

It is likely to cost about $8m per shipping lane for scanning equipment. There are 2,100 lanes in the US exporting ports.

The ports will also potentially have to be reconfigured to include screening equipment, the department observed.

In 2008, 9.8 million containers bound for the US had been shipped from 611 ports, according to the Government Accountability Office.