The disruption of a plot by al-Qaida in the Arabian peninsula to attack a US-based jet using what is being billed as an "improved" underwear bomb is likely to lead to increased security at American airports, the chief White House adviser on terrorism has indicated.

John Brennan, the deputy homeland security adviser to Barack Obama, gave a clear suggestion that additional security measures lay ahead across the country. Asked whether the interception of a bomb plot emanating from Yemen indicated holes in US security, Brannan told NBC that the examination of the IED device that is currently being carried out would lead to modifications.

"Whatever we learn from this IED, we're going to ensure that it's going to be incorporated into the measures that we take at airports, as well as any other avenues of approach that the would-be terrorists would take," he said.

The FBI is conducting forensic tests on the bomb as a first step towards discovering whether it would have cleared existing airport scanning systems. Dianne Feinstein, the Democratic senator for California who heads the Senate intelligence committee, gave an early hint when she said that she had been briefed about the device which she called "undetectable".

Just how major an escalation in the threat is posed by the bomb remains unclear. Security sources have told news agencies that it was a step up in levels of sophistication, particularly in its use of a more refined detonation system, and Brennan said "it was a threat from a standpoint of the design".

But CBS News quoted an unidentified law enforcement source who said that it was just a minor improvement on the explosives hidden inside the underpants of Umar Farouk Abdulmutallab, the would-be suicide bomber who tried to blow up a plane bound for Detroit on Christmas day in 2009.

What is certain is that the bomb contained no metal and might therefore have been capable of passing through metal-detectors at airports. Less clear is whether it would have passed the new generation of body scanners that have been partially introduced in larger airports.

The device was intercepted within the last 10 days, and was described as the product of successful international co-operation between the US and its partners. The focus is on al-Qaida's offshoot, al-Qaida in the Arabian Peninsula, AQAP, and speculation that the intelligence work was likely to have been done by Yemeni authorities possibly backed up by Saudi Arabia.

There was also speculation that the operation to foil the plot was linked to the drone attack at the weekend that killed the Yemeni al-Qaida leader Fahd al-Quso, wanted by the FBI for playing a part in the 2000 bombing of the USS Cole. Peter King, the Republican chairman of the House homeland security committee, told CNN that he had been told by the White House that "they are connected, they're part of the same operation".

Matthew Levitt, a counter-terrorism expert at the Washington Institute, said that the interception of the plot amounted to a significant achievement for US security agencies. He said: "The FBI is holding the device, which suggests that this was done by having boots on the ground. This was a sophisticated operation that shows we are making in-roads in serious places."

Levitt, who was involved as a senior analyst in the FBI's investigation into 9/11, said that it was natural to be sceptical in a presidential election year about security announcements. "But this was not political, it didn't come from the White House and my sense was that it was a really unique success," he said.

Levitt said that the spotlight would now be even more intense on Ibrahim Hassan al Asiri, AQAP's assumed bomb-making chief, who is thought to be hiding out in Yemen. Al Asiri is believed to have been the creator of the Detroit underwear bomb as well as explosives that were packed into printer cartridges bound for Chicago in 2010.

© Guardian News and Media 2012

[Toy airport security via nedrichards / Flickr]