WASHINGTON (CBS DC) — Chairman of the Joint Chiefs of Staff, Gen. Martin Dempsey, said that “open borders and immigration issues” have made Europeans and other foreigners who have joined ISIS an “immediate threat” to the U.S. and its allies domestically.

Dempsey told reporters in a Thursday Pentagon briefing that while ISIS would ultimately have to be defeated, the U.S. should concentrate on establishing allies in the eastern Syrian region to oppose the militant group that beheaded American journalist James Foley.

Dempsey said that the “immediacy” is the threat of non-Middle Easterners who joined ISIS but who have passports and access to return to Western countries.

“Those folks can go home at some point,” Dempsey said of Europeans that have joined the ISIS movement. “It’s why I have conversations with my European colleagues about their southern flank of NATO, which I think is actually more threatened in the near term than we are. Nevertheless, because of open borders and immigration issues, it’s… an immediate threat.”

“The immediacy is in the number of Europeans and other nationalities who have come to the region to become part of that ideology,” said Dempsey, referring to the ISIS fighters’ ability to return to their home countries.

Defense Secretary Chuck Hagel echoes Dempsey’s sentiments on ISIS, but both stopped short of calling for direct U.S. military action in the ISIS stronghold of eastern Syria.

“This is an organization that has an apocalyptic, end-of-days strategic vision and which will eventually have to be defeated,” said Dempsey. “To your question, can they be defeated without addressing that part of their organization which resides in Syria? The answer is no. That will have to be addressed on both sides of what is essentially at this point a non-existent border.”

Hagel said the U.S. is “very clear-eyed about ISIS, and that they are “beyond a terrorist group. They marry ideology, a sophistication of strategic and tactical military prowess.