The Obama administration may ask overseas partners to enhance security measures at airports and is weighing whether to do the same here at home to address deepening concerns that terrorists in war-ravaged Syria are trying to develop a new generation of bombs that could be smuggled onto commercial planes, ABC News has learned.
"[This threat] is different and more disturbing than past aviation plots," one source said.
The issue was discussed this past week at the White House during a meeting of top-level officials from intelligence agencies, sources said.
For months the Department of Homeland Security, FBI and other agencies have been quietly debating whether to boost the U.S. security posture and encourage overseas partners to take action too. The agencies have also been debating whether to make a public announcement on potential new security measures at airports.
The back-and-forth has been based on intelligence showing that a particularly extreme "subset" of terrorist groups in Syria was working alongside operatives from al Qaeda's prolific offshoot in Yemen to produce "creative" new designs for bombs, as one source put it.
Specifically, U.S. officials learned that associates of the al Qaeda affiliate in Syria -- the Al Nusrah Front -- and radicals from other groups were teaming up with elements of the Yemen-based group Al Qaeda in the Arabian Peninsula, which built such innovative devices as the "underwear bomb" that ultimately failed to detonate in a plane over Detroit on Christmas Day 2009.
Bolstered by more recent intelligence, U.S. analysts believe the "subset" of extreme terrorists in Syria could be looking to down a U.S.- or European-bound plane, with help from one of the thousands of Americans and other foreign fighters carrying U.S. and European passports who have joined Al Nusrah Front and other groups in the region.
Intelligence obtained by the U.S. government, however, has not indicated a specific target or a specific timeline.
While U.S. officials have been outspoken about the dangers posed by Al Qaeda in the Arabian Peninsula and – separately – the threat of foreign fighters in Syria, the latest intelligence shows that the two threats have bonded in an unusually powerful way, essentially creating a sum more worrisome than its parts.
After coming across the initial thread of intelligence earlier this year, U.S. officials, in regular consultation with the White House, began developing plans and potential security measures to address the threat. The development of those plans is now in its final stages, according to sources.