US warns of risks of identical airport security measures

"What we do not want is a cookie cutter approach -- where the same measures are in place everywhere -- because then terrorists can plan and work around them," she told a news conference in Toledo in central Spain.

Napolitano recommended using a wide range of security measures, including information sharing on suspected terrorists and detection technology like full body scanners, to protect passengers.

"We need all of those layers in sequence to maximize the ability to protect travelers from terrorist acts," she said, adding full body scanners were "a tool" but "there must be a combination of other measures".

"Nations decide for themselves the combination of these measures," she added.

Napolitano is meeting EU officials to try to convince the EU to install body scanners at its main airports for use by US-bound passengers.

The United States has accelerated the installation of the scanners at its airports since the attempted attack on Christmas Day on a jet bound for Detroit from Amsterdam, and Britain and the Netherlands have followed its example.

But other European nations like Germany have been more cautious.