40 Americans Who Went to Syria Have Returned: US Spy Chief

About 180 Americans have travelled to Syria to join Islamist militants and around 40 of them have returned to the United States, the U.S. National Intelligence director, James Clapper, said on Monday.

Clapper said not all those who went to Syria, where Islamic State militants and other factions are fighting each other and the forces of President Bashar al-Assad, had engaged in the Islamist campaign. Some might have been aid workers, he said.

The United States and its allies believe that more than 20,000 foreign fighters from more than 90 countries have gone to Syria. Islamic State forces have taken over large parts of Syria and neighbouring Iraq.

U.S. officials have expressed concern that some Americans, radicalised and trained to stage attacks in Syria, may wreak havoc when they come home. Clapper said he was not aware of any plots in which returning fighters had been involved.

He told a forum at the Council of Foreign Relations that as long as such travellers did not become engaged in violence, it was their "privilege as American citizens" to return to the United States.

Clapper said donations to extremist groups like Islamic State and al Qaeda affiliates by governments and private parties in Muslim countries had recently declined, and said that was partly because of stepped up oversight by governments in the region.

He reiterated that the priority of the United States and its allies in Syria now was the fight against Islamic State. But he said the United States still believed it was essential that Assad leave office because the "magnet for all of this extremism ... is because of him."

He acknowledged that U.S. efforts to recruit, vet and train "moderate" Syrian rebels would be a prolonged effort.

"The issue is the time it is going to take ... to get the ... firepower that will have an impact," he said.