International outrage over the grisly beheading of an American journalist is forcing President Obama’s hand in Iraq, intensifying pressure to confront ISIS in a broader way than the defensive airstrikes he has authorized so far.

In condemning the execution and expressing worldwide sorrow over the brutal slaying of James Foley Wednesday, Obama first made the point that the U.S. will continue to be “vigilant” and “relentless” in protecting Americans anywhere and pledged to act against the Islamic State of Iraq and Syria “standing alongside others.”

But in concluding his remarks, he went further, saying the U.S. and its “friends and allies” around the world will “continue to confront this hateful terrorism and replace it with a sense of hope and civility.”

Secretary of State John Kerry, who got to know Foley’s family after they enlisted his help in trying to find their son when he vanished in Syria two years ago, was more expansive about the U.S. response.

“Make no mistake: We will continue to confront [ISIS] wherever it tries to spread its despicable hatred,” he said. “The world must know that the United States of America will never back down in the face of such evil.”

ISIS and “the wickedness it represents must be destroyed, and those responsible for this heinous, vicious atrocity will be held accountable,” he continued.

Kerry’s comment immediately drew questions about exactly where and to what extent the U.S. would be willing to punish the terrorist group. News later Wednesday that the U.S. military earlier this summer had launched a failed mission to rescue Foley and other hostages held by ISIS underscored the administration's anger over his slaying.

State Department spokeswoman Marie Harf declined to outline future military or intelligence options at the administration's disposal but suggested that the U.S. may be in the process of recalibrating its fight against ISIS.

“We have reserved the right to take action to protect our people, including when our people have been harmed. That principle will guide what we do going forward,” she said.

Since the beheading video went public Tuesday, the U.S. military launched 14 more strikes around the Mosul Dam, and Harf pointed to Obama’s pledge to continue them.

“So those are all ongoing conversations about the best way to fight [ISIS],” Harf said.

Even as administration officials continued to stand by Obama's pledge not to put boots on the ground in Iraq, news broke that the Pentagon is weighing sending about 300 more troops to Baghdad to help fortify U.S. facilities, bringing the number of U.S. military service personnel in the country to 1,000.

Sens. John McCain, R-Ariz., and Lindsey Graham, R-S.C., continued their ongoing campaign to press Obama to go on offense against ISIS and support arming Syrian rebels.

"America and our allies and partners will only be secure when [ISIS] is defeated," they said in a statement. "That means we must get beyond half-measures, tactical responses, and defensive actions. We need to develop a comprehensive strategy – political, economic and military – to go on the offensive against ISIS, both in Iraq and Syria."

Charlie Dunlap Jr., a retired major general in the Air Force and a professor at Duke Law School’s Center on Law Ethics and National Security, said ISIS “grossly miscalculated” in killing Foley in such a gruesome public way.

The group's "grotesquely crude attempt at intimidation will hardly deter the U.S. or other nations from using force against them,” he said. “To the contrary, it will likely serve to justify even stronger actions.”

Americans overall support Obama's decision to launch airstrikes in Iraq by wide margins — 54 to 39 percent, according to a new Washington Post-ABC News poll.

Still, expanding airstrikes into Syria and sending combat troops remain overwhelmingly unpopular, especially within the liberal base of the Democratic party.

The Constitution Project, which seeks to limit presidential power to wage war without congressional consent, sent a letter to Obama Wednesday arguing that “the steady escalation of military intervention in Iraq has exceeded” Obama’s power and urging him to recall Congress from its summer recess to debate the issue.

Democrats, especially those in close races, want to avoid a vote expanding Obama's authority to wage war in Iraq, and the president also would likely recoil from the optic.

At least in the near-term, with the midterm elections just a little more than two months away, veteran foreign policy experts don’t expect any bold expansion of the U.S. fight against ISIS.

Faysal Itani, a resident fellow at the Atlantic Council’s Rafik Hariri Center for the Middle East, predicts the beheading won’t change Obama’s calculus significantly.

“President Obama has quite clearly defined the mission in Iraq as mainly containment,” he said. “He is not trying to chase [the Islamic State] back to its place of origin. He realizes that would be quite costly.”

Kerry’s more aggressive statement likely reflects his more activist view of U.S. foreign policy.

"He can do that within limits," Itani said, noting that it's unlikely that Kerry's comments signal a shift in Obama's strategy or thinking.

A containment policy, Itani argued, would do nothing to weaken ISIS because its strength is based on control of territory.

In addition to supporting the Iraqi and Kurdish forces, the U.S. should be arming and training Syrian rebels and help them weaken Syrian President Bashar Assad’s regime, he said.

“As long as [the rebels] are waging a two-front war, then they are not going to be able to weaken the Syrian regime” or stop ISIS from consolidating land and power, he said.