"It's more than aspirational," a U.S. official told The Wall Street Journal. "They're trying to make this happen."
The U.S. Department of Homeland Security warning to foreign governments and U.S. and international airlines "did not relate to an imminent or specific threat," White House spokesman Jay Carney told reporters Wednesday.
But the possibility of explosive devices surgically implanted in terrorists' abdomens, buttocks and breasts will prompt additional security measures at U.S. airports and overseas airports serving U.S. destinations, the U.S. Transportation Security Administration said in a statement.
The new measures could include increased use of behavior-detection techniques such as agents studying passengers for nervous behavior and conducting airport interviews, pat-down searches, and efforts to detect traces of explosive materials by swabbing skin and clothing and using explosives-sniffing dogs and machines, the TSA said.
"These measures are designed to be unpredictable, so passengers should not expect to see the same activity at every international airport," spokesman Greg Soule told The New York Times.
Regular scanning equipment, including full-body scanners, is not designed to penetrate the skin, so it would not be able to detect implanted devices.
Security was already heightened after the May 2 U.S. killing of al-Qaida leader Osama bin Laden, officials said.
The latest intelligence links the "belly bombs" to al-Qaida's branch in Yemen, where a popular uprising against President Ali Abdullah Saleh and tribal clashes have created a security vacuum, giving the branch increased license, officials said.
Al-Qaida in the Arabian Peninsula, which operates in Yemen and Saudi Arabia, claimed responsibility for the botched Christmas Day 2009 attempt to down Detroit-bound Northwest Airlines Flight 253 with a plastic bomb sewn into the bomber's underwear.
Even so, implanting a bomb powerful enough to do serious damage would be difficult, homeland security expert James J. Carafano of the Heritage Foundation think tank told the Times. It would also be hard for a passenger to position himself properly in a plane to cause truly catastrophic destruction, he said.
Trends Research Institute Director Gerald Celente said four days after bin Laden's killing the Obama administration would soon seek to instill fear with "the terror card" to boost his poll ratings and get Americans' minds off the struggling economy.
"The terror bandwagon is rolling and it's going to roll right through to Election Day," Celente told "The Alex Jones Show."