TALLINN, Estonia — President Obama vowed on Wednesday to punish the Sunni militants whose videotaped beheadings of two American journalists he said had “repulsed” the world, saying the United States would lead a regional and international coalition to beat back the terrorists.
“Our objective is clear, and that is: degrade and destroy ISIS so that it’s no longer a threat, not just to Iraq but also to the region and to the United States,” Mr. Obama said, using an alternative acronym for the Islamic State in Iraq and Syria. He was speaking at a news conference here on the eve of a NATO summit meeting in Wales, as pressure built for him to articulate a broader military strategy to take on the ISIS militants.
“It’s not only that we’re going to be bringing to justice those who perpetrated this terrible crime against these two fine young men,” the president said. “The United States will continue to lead a regional and international effort against the kind of barbaric and ultimately empty vision” the group represents.
Mr. Obama’s strongly worded statement came after he drew criticism from allies and foes last week, when he said that he had not yet developed a strategy for confronting ISIS in Syria. American airstrikes in Iraq, the president said on Wednesday, had “borne fruit” by “blunting the momentum” of the militants in that country and averting the humanitarian disasters it had threatened to spark.
He spoke just hours after the White House said intelligence agencies had analyzed a video showing the beheading by an ISIS fighter of Steven J. Sotloff, a 31-year-old freelance journalist, and considered it authentic.
“Whatever these murderers think they will achieve by killing innocent Americans like Steven, they have already failed,” Mr. Obama said in his first comments on Mr. Sotloff’s killing since the video was released.
“We will not be intimidated,” the president said. “Their horrific acts only unite us as a country and stiffen our resolve to take the fight against these terrorists.”
Secretary of State John Kerry also expressed outrage at what he called the “unfathomable brutality” of the militant who killed Mr. Sotloff, describing Mr. Sotloff as an intrepid journalist “taken from us in an act of medieval savagery by a coward hiding behind a mask.”
Mr. Kerry said those responsible for the killings of Mr. Sotloff and James Foley, a journalist shown beheaded in an ISIS video released Aug. 19, would be held accountable by the United States, “no matter how long it takes.”
The video pressure on the president to order military strikes on ISIS in its sanctuary in Syria.
Mr. Obama said he was not yet ready to order such action, saying he wanted to be sure that the mission would be effective and that allies at home and abroad supported it.
“It is very important from my perspective that when we send our pilots in to do a job, that we know that this is a mission that’s going to work, we’re very clear what our objectives are, what our targets are, we’ve made the case to Congress and we’ve made the case to the American people, and we have allies behind us,” Mr. Obama said, “so that it’s not just a one-off.”
Pressed on whether he was talking about the elimination of ISIS, Mr. Obama suggested he was seeking instead to limit the group’s reach. He said that his goal was to ensure that ISIS “is not an ongoing threat to the region,” and that the group was “degraded to the point where it is no longer the kind of factor that we’ve seen it being over the last few months.”
Mr. Obama said that if the United States is joined by the international community, “we can continue to shrink ISIL’s sphere of influence, its effectiveness, its financing, its military capabilities to the point where it is a manageable problem.”
In the latest video, Mr. Sotloff is shown kneeling in the same fashion as Mr. Foley was in a video released two weeks earlier, with a masked figure standing above and wielding a knife. Mr. Sotloff addresses the camera and describes himself as “paying the price” for Mr. Obama’s decision to strike the group in northern Iraq.
The president was briefed on the video Tuesday before his departure for Estonia.
His remarks, which were made at a joint news conference with President Toomas Hendrik Ilves of Estonia, came at the start of a three-day visit to Europe that was choreographed to project a strong response by Mr. Obama and European allies to Russia’s increasingly bellicose moves in eastern Ukraine. But with the situation there changing rapidly and the surfacing of the second ISIS video, the trip is instead serving to showcase the vexing array of pressures weighing on the president to move more decisively on crises around the globe.
Mr. Obama arrived in Estonia on Wednesday for a day of private meetings with Baltic leaders and public statements meant to reassure allies – particularly those bordering Russia – that the United States and Europe are serious about defending them from their newly aggressive neighbor.
He was scheduled to travel to Wales later in the day for a NATO summit meeting, at which members are expected to endorse a rapid-reaction force capable of deploying quickly to Eastern Europe, their strongest response yet to Russia’s stealth military intervention in Ukraine.
Confronting ISIS is not on the formal agenda for the NATO meeting, but it is very much an issue expected to be addressed on the sidelines, where Mr. Kerry and Defense Secretary Chuck Hagel will be working to enlist help from allies in developing a strategy to counter the militant group.