WASHINGTON — U.S. intelligence officials are concerned that al-Qaida is trying to develop a new and improved bomb that could go undetected through airport security.

There is no indication that such a bomb has been created or that there’s a specific threat to the U.S., but the Obama administration on Wednesday called for tighter security measures at foreign airports that have direct flights to the U.S.

American intelligence has picked up indications that bomb makers from Yemen-based al-Qaida in the Arabian Peninsula have traveled to Syria to link up with the al-Qaida affiliate there known as the Nusra Front, according to a counterterrorism official who spoke on condition of anonymity because he was not authorized to speak publicly about the matter by name. The enhanced security measures have been in the works for the past month, he said.

Al-Qaida in the Arabian Peninsula long has been fixated on bringing down airplanes with hidden explosives.

It was behind failed and thwarted plots involving suicide bombers with explosives designed to be hidden inside underwear and explosives secreted inside printer cartridges shipped on cargo planes.

Over the past year, Americans and others from the West have traveled to Syria to join the fight against the Syrian government. The fear is that fighters with a U.S. or other Western passport, who therefore are subject to less stringent security screening, could carry such a bomb onto an American plane.