“Unless the money is actually in the U.S. financial system, you have to point out to these governments where the money is going and try to work with them to make sure it goes to legitimate groups,” said one U.S. official who spoke with The Washington Times on the condition of anonymity because of the sensitivity of intelligence related to tracking such money.

“The U.S. can’t shut down bank accounts in Kuwait or Qatar,” the official said. “We can tell them, ‘Look at what this person is doing.’”

The approach has worked with variable success over the past decade, during which U.S. authorities have worked closely with counterparts in such nations as Kuwait, Qatar and Saudi Arabia to choke off streams of cash to al Qaeda’s core leadership in Pakistan and Afghanistan.

But when it comes to stemming the flow of aid to Salafist and al Qaeda-linked groups inside Syria, the strategy has been less successful — suggesting authorities in the Gulf now may see American pressure for such action as less worthy than previous calls to block cash to al Qaeda.