Indications that ISIS or an affiliated terror group took down a Russian airliner over Egypt don't just raise the possibility of one of the worst terror attacks since September 11, 2001.

They also represent a possible turning point in what is now a generational battle against terrorism: ISIS may have made the decision to escalate from military operations aimed at creating a caliphate in Iraq and Syria and inspiring followers to stage isolated terror attacks on the West to attacking soft, civilian targets in mass casualty strikes.

President Barack Obama said Thursday it's possible a terrorist bomb brought the plane down.

"I think there's a possibility that there was a bomb on board," Obama said in an interview with Dave Ross of CBS News affiliate KIRO in Seattle.

He said the current intelligence isn't definitive enough to say exactly what felled the aircraft and noted that security procedures in place in the region were different than in the United States.

"We're going to spend a lot of time just making sure our own investigators and own intelligence community find out what's going on before we make any definitive pronouncements," he said. "But it's certainly possible that there was a bomb on board."

The disaster, which killed more than 200 mainly Russian civilians on a flight from the Egyptian resort of Sharm el-Sheikh to St. Petersburg, also presents the United States with a new flurry of complicated security, diplomatic and political questions.

The U.S. government has largely kept American civilians safe from terrorism during the 14 years since 9/11, and President Barack Obama has claimed that record and the crushing of core al Qaeda under his watch of one of his top achievements.

But the possibility that ISIS is behind the plane crash raises the specter of a new potential for devastating attacks on Americans. If another Islamist group has acquired the motivation and the capacity to attack civilian airliners, a future target could be U.S. jets.

"It is a long war and you we have just seen maybe a very significant turn and escalation in that war," said Aaron David Miller, a former U.S. Middle East peace negotiator now with the Wilson Center in Washington.

We haven't yet found a way -- and I think it's going to be extremely difficult to hermetically seal the nation, abroad or here at home, against these kinds of attacks," he said on CNN's "New Day."

How to respond to the possibility of an expanded ISIS threat -- if confirmed by investigators -- will likely vex the administration and increase pressure on U.S. intelligence agencies to forestall a similar strike against a U.S. target.

An expanded and potentially more lethal threat from ISIS to Americans could also scramble the assumptions that are currently underpinning Obama's policy towards the region.

Guided by his desire to extricate the United States from costly, intractable foreign wars, he has been loath to jump into new ones.

Initially, he ridiculed the idea that ISIS would evolve into the same kind of global threat as al Qaeda, once referring to the group as a junior varsity organization. The President has also argued that the events of the last decade prove that Washington has a limited capacity to dictate outcomes in a Middle East torn by conflict, where traditional borders and ideas of nationhood are being ripped apart in a tide of sectarianism.

So his decision to deploy troops back to Iraq after ending the war, firstly to train and assist Iraqi forces and then to use air power to target ISIS, were taken reluctantly. And the President's decision last week to send 50 Special Operations forces to help U.S.-backed rebels in Syria -- putting boots on the ground, as he eventually did in Iraq as well -- was a step that he had previously told Americans he would never take.

Now, the White House might be forced into yet another exhaustive review of its goals and strategies in the region.

Source: cnn