The number of foreign fighters traveling to Syria and Iraq to join the Islamic State or other extremist groups continues to rise despite months of bombardment by the U.S. and its allies.
U.S. counterterrorism officials plan to tell the House Homeland Security Committee on Wednesday that more than 20,000 foreign fighters from more than 90 countries have gone to the region.
Nick Rasmussen, director of the National Counterterrorism Center, will tell the committee that at least 3,400 of the foreign fighters in Syria came from Western countries, and that they include over 150 U.S. citizens or residents. A copy of his testimony was made available to the media.
He says the "majority'' of those arriving in Syria now are joining Islamic State formations in Syria and Iraq.
Western officials have long been worried that those fighters, especially the ones with U.S. and European passports, could return home radicalized and well-trained and commit terrorist attacks.