Carter said defense ministers from more than two dozen countries gave a "broad endorsement" of a refined US plan for defeating the militants.
After a meeting at NATO headquarters, Carter told reporters that nearly all participants either promised new military commitments or said their governments would consider new contributions.
"I'm very pleased that so many nations have stepped up and answered the call, even in recent days," Carter said. "But my challenge to coalition members to accelerate our military campaign will not end today, any more than America's resolve to lead and make more contributions itself will end today. It will continue."
He said that 60 per cent of the coalition members have increased their contributions, and another one-third said they will seek authority from their governments to do more.
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In public remarks at the start of the meeting with coalition members, Carter cast the talks as an historic effort to hasten the demise of IS, which has proved resilient in Iraq and Syria and is spreading to Afghanistan, Libya and elsewhere in the greater Middle East.
"We will all look back after victory and remember who participated in the fight," he said.
In Munich, Germany, US Secretary of State John Kerry was trying today to find a way to halt what amounts to a parallel war in Syria. Five years of civil war have pitted President Bashar Assad's government, backed by Russia and Iran, against an array of weakened opposition groups, some supported by the United States.