WASHINGTON - For three years, President Barack Obama has resisted the pull of potential U.S. military action in Syria.

He has held firm even as the civil war's death toll climbed toward 200,000, the Syrian government used chemical weapons against civilians and Islamic State militants strengthened amid the chaos.

Now Obama must decide whether the extremist group's murder of American journalist James Foley, as well as the broader threat the group could pose to U.S. interests, should change his cautious calculus.

Pressure is coming from his own military leaders to go after the Islamic State inside Syria. But he must weigh that against his aversion to the risks that could come with plunging the United States into a country torn apart by an intractable internal conflict.

White House officials have suggested that airstrikes in Syria are an option, though the officials say specific military proposals has not yet been presented to the president.

"We're actively considering what's going to be necessary to deal with that threat, and we're not going to be restricted by borders," said Ben Rhodes, Obama's deputy national security adviser. "We've shown time and again that if there's a counterterrorism threat, we'll take direct action against that threat, if necessary."

Even before Foley's murder, Obama found himself on far different footing in the Middle East than he probably expected in the sixth year of his presidency.

After running for the White House on a pledge to end the Iraq war and then making good on that promise in late 2011, Obama thrust the U.S. military back into Iraq this month with a limited airstrike campaign against Islamic State targets.

Obama has said he will not send U.S. combat troops to another ground war in the Mideast. But expanding the airstrikes in Iraq and broadening them to include Syria could mean a lengthy American military commitment in the region that could consume much of Obama's remaining time in office.

"What we should have learned over the past dozen years in that part of the world is that the use of military power is very unpredictable," said Stephen Walt, a professor of international affairs at Harvard's John F. Kennedy School of Government.

That may be particularly true in Syria, where President Bashar Assad's government is warring with opposition forces. Unlike in Iraq, the battle lines are more clearly drawn. Syria has a host of military players in close proximity to each other, including the Islamic State, the al-Qaida-linked Nusra Front, mainstream Western-backed rebels and pro-government forces.

The Islamic State is among the groups fighting Assad, meaning a U.S. campaign to weaken the extremists could actually strengthen a leader the White House has sought to push from office.

Obama could try to counteract that uncomfortable dynamic by also taking strikes against Assad, though that could put the U.S. on the hook for the kind of long-term commitment to rebuilding Syria that he has tried to avoid.