Coalition air strikes in Syria and Iraq have halted or reversed the momentum of jihadist group Daesh, US Secretary of State John Kerry was quoted by BBC as saying.
Speaking after talks in London between 21 coalition states, Kerry said about half the group's leaders had been killed since strikes began in August.
Kerry said: "In recent months we have seen definitively... momentum halted in Iraq and in some cases reversed."
After nearly 2,000 air strikes, ground forces had reclaimed some 700 sq km (270 sq m) of territory, he told the news conference.
Giving details of military operations against Daesh, Kerry said the coalition was "taking out" its fighters "in the thousands thus far, single digits but thousands".
"About 50% of the top command" had been eliminated, he said.
Hundreds of vehicles and tanks had been destroyed, he continued, as had nearly 200 oil and gas facilities being used by Daesh to fund its operations, and more than 1,000 IS military sites.
But Iraqi Prime Minister Haider al Abadi warned falling oil prices could hurt Iraq's fighting capacity.
Stressing that the collapse in the oil price had been "disastrous", Prime Minister Abadi pointed out that oil revenue accounted for 85 percent of Iraq's budget.
"We don't want to see a reverse of our military victory because of our budget and fiscal problems and we have been assured that every member of this coalition will stand with Iraq in its fight against Daesh," he said.
Abadi thanked the coalition for providing training to his forces but said it needed more help with the supply of weapons.
British Foreign Secretary Philip Hammond had warned at the start of the meeting that it could be months before Iraq was ready to take the offensive to Daesh.
But the country had clearly demonstrated its commitment to defeating radical Islamists who preach hatred, he said at the concluding news conference.
"So long as Iraq delivers on its commitments, the international community will stand behind it," he said.
Among other issues discussed at the one-day conference was that of stopping foreign fighters travelling to the war zone.
Source: MENA