The United States is calling for tighter security measures at some foreign airports after reports of a new al-Qaida effort to create a bomb that would go undetected through airport security, according to Reuters.

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

The U.S. has been planning for additional measures for the past month, a counterterrorism official said Wednesday, adding there was no immediate threat that led to the announcement by the Homeland Security Department that it was requesting tighter security abroad, according to Reuters.

"We are sharing recent and relevant information with our foreign allies and are consulting the aviation industry," Department of Homeland Security Secretary Jeh Johnson said in a statement, Reuters reported.

American intelligence has picked up indications that bomb makers from al-Qaida's Yemen affiliate have traveled to Syria to link up with the al-Qaida affiliate there, Reuters reported. The groups are working to perfect an explosive device that could foil airport security, the counterterrorism official said.

Al-Qaida's affiliate in Yemen, called al-Qaida in the Arabian Peninsula, long has been fixated on bringing down airplanes with hidden explosives, according to Reuters. It was behind failed and thwarted plots involving suicide bombers with explosives designed to hide inside underwear and explosives hidden inside printer cartridges shipped on cargo planes.

It wasn't clear which airports were affected by the extra security measures, but industry data show that more than 250 foreign airports offer nonstop service to the U.S., including Paris' Charles de Gaulle Airport, Amsterdam's Schiphol Airport and the United Arab Emirates' Dubai International Airport, Reuters reported.