NEWPORT, Wales: NATO leaders grappled Thursday with whether the alliance has a role in containing a mounting militant threat in the Middle East, as heads of state converged in Wales for a high-stakes summit also focused on the crisis in Ukraine and next steps in Afghanistan.

President Barack Obama and British Prime Minister David Cameron declared that their nations would “not be cowed” by militants from the Islamic State (IS) group who have claimed responsibility for killing two American journalists. They also challenged NATO to not turn inward in the face of the threat.

“Those who want to adopt an isolationist approach misunderstand the nature of security in the 21st century,” Obama and Cameron wrote in a joint editorial in the Times of London. “Developments in other parts of the world, particularly in Iraq and Syria, threaten our security at home.”

Obama, Cameron and dozens of other NATO leaders met on a golf resort in Wales for the two-day summit. Leaders here also planned to commit to a more robust rapid response force on its eastern flank, which would aim to serve as a deterrent to Russian aggression.

Yet much of the action was to take place on the sidelines of the summit, where the American and British leaders were expected to drum up support for an international response to confronting the IS militants in Iraq and Syria.

Arriving at the summit site on Thursday, NATO Secretary-General Anders Fogh Rasmussen said he believes the broader international community “has an obligation to stop the IS from advancing further,” but noted that the alliance hasn’t received any request for help.

“I’m sure that if the Iraqi government were to forward a request for NATO assistance, that would be considered seriously by NATO allies,” Rasmussen said.

The militants have claimed responsibility for murdering two American journalists, releasing gruesome videos of their beheadings. Both the US and Britain are deeply concerned about the potential threat to their homelands that could come from the foreign fighters who have joined the violent IS.

Cameron on Monday proposed new laws that would give police the power to seize the passports of Britons suspected of having traveled abroad to fight with terrorist groups.

The US began launching airstrikes against IS targets in Iraq last month, and both the US and Britain have been making humanitarian aid drops to besieged minority groups there. Cameron said that he hadn’t ruled out joining the US in airstrikes, but added that the priority was to support those already fighting the militants on the ground.

“We need to show real resolve and determination, we need to use every power and everything in our armory with our allies — with those on the ground — to make sure we do everything we can to squeeze this dreadful organization out of existence,” Cameron told the British network ITV.