Whether true or not, U.S. intelligence officials will only divulge to media that they believe a “small handful” of Americans are currently fighting as soldiers within the Islamic State.

But one British parliamentarian believes that the terrorist “caliphate” now boasts more British Muslim recruits than are currently enlisted to fight in Britain’s own armed forces.

Member of Parliament Khalid Mahmood of Birmingham UK told Newsweek on Wednesday that Sunni extremists have successfully recruited 1,500 or more British Muslims to fight in Iraq and Syria over the last three years – at least.

“If you look across the whole of the country [of Syria], and the various communities involved, 500 going over each year would be a conservative estimate,” Mahmood said, referencing the recruitment of fighters dating from the outset of the conflict in Syria.

Here’s more from Newsweek:

The UK Foreign Office said that they believe over 400 individuals have travelled to Syria since the uprising began, but said that they could not give exact numbers. However Mahmood described such low estimates as “nonsense” and said that the British government was failing to deal with the problem of home-grown extremists. “We’ve not concentrated on the prevention work, we haven’t invested enough in de-radicalisation. It’s tragic, somebody’s got to wake up to it.” The role of British jihadists fighting in the Middle East has been brought into sharp focus after Islamic State released a video showing the apparent beheading of US journalist James Foley by a masked jihadist who spoke with a British accent.

American officials confirmed Wednesday that it was indeed Foley whom the terrorist murdered before the camera.

Also on Wednesday, NBC News said U.S. officials do not believe Americans have been persuaded to join the Islamist extremists in numbers approaching those Mahmood believes have been recruited out of Britain.

“The officials, who spoke with NBC News on condition of anonymity on Wednesday, say they base that opinion on analysis and a string of recent arrests and investigations of U.S. citizens who have sought to join the group that is simultaneously fighting government forces in both Iraq and Syria,” the network reported.

Yet, at least in terms of what’s been made public, no solid information can confirm the assumptions of American intelligence when it comes to the Islamic State’s success in bringing in fighters into Iraq and Syria from the U.S. “The [same U.S.] official emphasized that the U.S. has no specific intelligence identifying any Americans as having fought with ISIS.”

That report also observed that even FBI Director James Comey has recently confessed that it’s impossible for U.S. intelligence to get a solid read on how many Americans in general – not just jihadists – have traveled to Syria. “When I give you the number of more than 100, I can’t tell you with high confidence that’s a 100 of 200, that’s a 100 of 500, that’s a 100 of a 1,000 or more, because it’s so hard to track,” he said.