It is one thing for President Barack Obama to propose an international coalition to "destroy" Islamic State.
It is another to build it in the Middle East, scorched by sectarianism and raging proxy wars, with American credibility eroded by misadventures in Iraq and where allies bristle at what they view as Obama's misfiring diplomacy.
But the president is promising action.
"What we've got to do, is make sure that we are organizing the Arab world, the Middle East, the Muslim world along with the international community to isolate this cancer," he said in Estonia Wednesday.
Islamic State's lair in Syria and Iraq has alarmed the region and may already have jumbled political calculations.
Iran for instance pulled support for Prime Minister Nuri al-Maliki in Iraq's post-electoral chaos, after his sectarianism was blamed for the rise of IS.