Representatives from the 23 countries of the US-led coalition battling the jihadists' self-declared "caliphate" gathered in Rome to assess and renew their efforts.
Italian Foreign Minister Paolo Gentiloni and US Secretary of State John Kerry told their allies that, since their meeting six months ago, the IS group had suffered setbacks in its core territory in Syria and Iraq.
But the hosts warned that the group is adapting to the pressure on its heartland and is redirecting efforts to Libya, where it has seized new territory, and to attacks like those in Paris, Ankara and San Bernadino, California.
"We're here to recommit, we're here to re-evaluate, we're here to make judgements about things we have started that we could do better," he said.
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Gentiloni said the challenge facing the coalition of mainly Western and Arab nations is stark.
"We know that we have in front of us an organisation that is very resilient and able to plan strategically and so we should not underestimate it," he said.
"If anything we need to be ever more wary and more watchful because we know that the more Daesh is squeezed in its core territories the more tempted it is pursue its terrorist activities elsewhere," he warned, using an Arabic name for IS.
Italy has taken the lead with the coalition in planning for how to address the IS threat a short boat ride from its southern shores in the Libyan city of Sirte.
"In the past few months the threat in our own homelands has taken on a new more dangerous dimension requiring the coalition's focused and coordinated attention," he added.
Washington likes to claim that it has built a 66-nation coalition to fight the IS group - the latest country to join this week was Afghanistan, Kerry said.