As the U.S. launches Operation Odyssey Lightning against the Islamic State group in Libya, a fourth front in the war against the brutal militant group, U.S. commanders are casting a wary eye on a possible fifth front: the Asia-Pacific.

The U.S. is launching strikes in Syria, Iraq, Afghanistan and now Libya, but military leaders and strategists are alarmed by waves of violence and signs that countries with large Muslim populations like the Philippines and Bangladesh could be ISIS’s next global stronghold.

In a July 27 speech to the Rebuild Japan Initiative Foundation, U.S. Pacific Command head Adm. Harry Harris said the region would need to work together to stop ISIS from metastasizing into what the U.S. military calls the Indo-Asia-Pacific region.

“I often talk about the U.S. strategic rebalance to this region,” Harris said. “Regrettably, I believe that ISIL is also trying to rebalance to the Indo-Asia-Pacific. To halt the Islamic State’s cancerous spread in Asia, we can’t work alone. We must work together.