That came as President Donald Trump boasted that the extremists will soon have lost all their territory in Syria as he addressed representatives from more than 70 countries in Washington to discuss ways in the battle Islamic State, also known as ISIS, after Trump stunned many in December by declaring victory and ordering all 2,000 American troops out of Syria.
Trump said that US-led troops and Kurdish allies had "liberated virtually all of the territory" from the jihadists who once controlled a vast stretch of Syria and Iraq in a self-styled caliphate.
"It should be formally announced some time next week that we will have 100 percent of the caliphate," Trump said.
"Remnants - that's all they have, remnants - but remnants can be very dangerous.
"Rest assured, we'll do what it takes to defeat every ounce and every last person within the ISIS madness and defend our people from radical Islamic terrorism."
The conference came amid behind-the-scenes efforts to manage the unintended consequences of the impending US pullout, including keeping the peace between Turkey and Kurdish fighters and finding a solution for hundreds of foreign jihadists behind bars in Syria who Washington says should be repatriated.
But the one-day Global Coalition to Defeat ISIS did not produce major announcements. And US leaders were focused too on domestic priorities, with Trump using the occasion to vow a hard line on immigration and Secretary of State Mike Pompeo taking unsubtle digs at previous president Barack Obama.
The conference did not include representatives of Syria's Bashar al-Assad or Russia and Iran, which have said they seek to defeat the Islamic State group as they shore up the dictator's rule.
Opening the conference, Pompeo described Trump's troop pullout as a "tactical change" with extremists increasingly scattered around the world.
"It is not a change in the mission," he said, but "our fight will not necessarily always be military led. We are entering an era of decentralized jihad, so we must be nimble in our approach as well."
Officials say that the US withdrawal will happen, though at a slower pace than Trump intended.
The US representative who was in charge of the coalition, Brett McGurk, resigned along with defense secretary Jim Mattis in protest over Trump's decision.
And Trump's own intelligence chief, Dan Coats, warned last week before Congress that the Islamic State group would try to stage a comeback as troops withdraw.
Hoping to avoid the worst outcomes, Pompeo also asked US partners to step up sharing of intelligence and to make up a US$350 million (HK$2.73 billion) shortfall in a fund intended to stabilize Iraq.