MANILA, Philippines?Deploying some 660 U.S. troops may help control the Muslim extremist group that has plagued the Philippines for a decade, but the escalating American involvement will test ties between Washington and one of its closest allies in Southeast Asia.

President Gloria Macapagal Arroyo welcomes the U.S. military buildup, saying it could help deliver a fatal blow to the Muslim extremist group Abu Sayyaf, which has been linked to Osama bin Laden’s al Qaeda network.

But the military mission could also further inflame the country’s Muslim minority and alienate some of the president’s leftist supporters.

Defense Secretary Donald Rumsfeld said at the Pentagon that up to 250 U.S. troops were in the country and “several hundred more” would follow. A “small number” were in an area where Philippine forces have been battling Abu Sayyaf rebels.