President Barack Obama, in a major reversal, moved Wednesday to deepen the U.S. military role in the volatile Middle East, vowing to wage an unrelenting counterterror effort that will rely on airstrikes to target Islamic State fighters in both Iraq and Syria.

Obama outlined his strategy, which also includes training and arming Syrian rebels, in a high-stakes address to the nation Wednesday night. Obama said the objective is to “degrade and ultimately destroy” the Islamic State group.

“This counterterrorism campaign will be waged through a steady, relentless effort to take out ISIL wherever they exist using our air power and our support for partner forces on the ground,” Obama said, using an alternative name for the group.

Until now, the U.S. launched airstrikes against the group only within the borders of Iraq, whose government invited the American military to take that step. But officials have said in recent days that the Islamic State, which also controls territory in Syria, must be viewed as one group, not two separate entities split by a border.

Ahead of Obama’s remarks, congressional leaders grappled with whether to support his request to arm the Syrian opposition and if so, how to get such a measure through the fractured legislature.

Obama’s plans amount to a striking shift for a president who has steadfastly sought to wind down American military campaigns in the Middle East and avoid new wars. That stance has been notable in Syria, where Islamic State militants have taken advantage of the instability created by a three-year civil war and now operate freely in areas near and across the Iraqi border.

Story compiled with information from The Associated Press.