US intel confirms journalist execution video ‘authentic,’ Obama vows ‘relentless’ fight against ISIS

President Obama, reacting to the brutal execution of an American journalist by Islamic State terrorists, said Wednesday that the militant organization has “no place in the 21st century,” as U.S. intelligence analysts confirmed the authenticity of a video showing the journalist’s beheading.

The president, in brief remarks from Martha’s Vineyard, said the video of James Foley’s death “shocks the conscience,” while vowing to continue the fight against the organization which has taken root across swaths of Iraq and Syria. He called for a “common effort” across the Middle East to “extract this cancer so it does not spread.”

“The United States of America will continue to do what we must do to protect our people,” Obama said. “We will be vigilant and we will be relentless.”

Military analysts and U.S. lawmakers also say the execution should be a wake-up call to the need to dismantle the militant organization.

The remarks come after the White House National Security Council released a brief statement saying the intelligence community reviewed the video and has “reached the judgment that this video is authentic.” Obama said he spoke with Foley’s parents earlier Wednesday.

The beheading marks the first time the Islamic State — also known as ISIS, or ISIL — has killed an American citizen since the Syrian conflict broke out in March 2011, upping the stakes in an increasingly chaotic and multilayered war.

“America got a glimpse of exactly who they are,” House Intelligence Committee Chairman Mike Rogers, R-Mich., told Fox News on Wednesday. “This is a group you need to deal with.”

Sen. Marco Rubio, R-Fla., called the “brutal execution” of a hostage “the clearest indication to date that ISIL has declared war on the United States.”

The militants in the video railed against U.S. airstrikes in Iraq and threatened to kill a second American journalist, depending on Obama’s “next decision” – an apparent reference to U.S. military policy in the region.

The video puts pressure on the White House to weigh the risks of ramping up airstrikes in Iraq targeting the Islamic State, and the possibility that militants could kill more Americans in response.

But in an indication that the U.S. response is not changing, a U.S. official said American fighter jets and drones conducted nearly a dozen strikes in Iraq since Tuesday.

Rogers and others said the video only underscores the need to develop a clear strategy for defeating the group. Rogers said this week’s success, for instance, in helping Iraqi and Kurdish forces retake the Mosul Dam from militants must be part of a “bigger strategy.”

“That ought to get us off our backsides and get to work on dismantling this organization. It’s dangerous,” he told Fox News.

More From FoxNews: