(Adds NATO ready to assist Iraq, Jordan, returning fighters)
By Phil Stewart and Julien Ponthus
NEWPORT, Wales, Sept 5 (Reuters) - The United States said it had created a "core coalition" on Friday to battle Islamic State militants in Iraq, calling for broad support from allies and partners around the world but ruling out committing ground forces.
President Barack Obama sought to use a NATO summit in Wales to enlist allied support in a campaign to destroy the Islamist militants but as the summit drew to a close it remained unclear how many nations might join Washington in air strikes.
Secretary of State John Kerry and Defence Secretary Chuck Hagel told foreign and defence ministers from 10 nations at a hastily arranged meeting that there were many ways they could help, including training and equipping the Iraqis.
British and German ministers warned that it would be a long campaign to push the Sunni militants back after stunning gains they have made in Syria and Iraq, drawing volunteers from many countries including in the West.
NATO announced plans for allies to share more information on westerners fighting for IS - who U.S. and European security officials see as a major risk to national security when they return home. NATO may also coordinate airlifts by member states to deliver assistance to Iraq.
"We need to attack them in ways that prevent them from taking over territory, to bolster the Iraqi security forces and others in the region who are prepared to take them on, without committing troops of our own," Kerry told the meeting.
"Obviously I think that's a red line for everybody here: no boots on the ground."
Hagel told ministers from Britain, France, Germany, Canada, Australia, Turkey, Italy, Poland and Denmark that they, with the United States, formed the core group for tackling the Sunni militant group.
"It is the core group that will form the larger and extended coalition that's going to be required to deal with this challenge," he said.
Kerry said he hoped the allies could develop a comprehensive plan for combating IS in time for this month's annual U.N. General Assembly session in New York.
The threat posed by returning foreign fighters was "a challenge to every country here", Kerry told the ministers.
Britain raised its terrorism alert last week to its second-highest level over the threat posed by IS, meaning it assessed a strike was "highly likely".
Turkey, which attended the talks, has been struggling to staunch a flow of foreign jihadists across its border with Syria. Hagel travels to Turkey next week.
British Prime Minister David Cameron and French President Francois Hollande, the leaders of Europe's main military powers, told Obama in private meetings that Washington had to do more than simply order air strikes on IS targets in Iraq and needed an overall strategy, European officials said.
"It can't be just 'let's go and bomb a few targets and see what happens'," said one Western defence official familiar with the talks between the allied leaders.
France said this week it was ready to engage in all aspects of the fight against IS, including potentially military action. British Foreign Secretary Philip Hammond said on Friday that London had not yet decided on any involvement in air strikes.
A British official, speaking on condition of anonymity, said: "There is a growing sense that this is going to take more than we are doing... but it needs to be a measured, cautious approach."
A statement issued by Hagel and Kerry after the meeting said the coalition would need to go after IS finances, including any trade in petroleum products, and discredit its ideology.
The Europeans have called for a global strategy to combat the Islamic State threat, involving a new Iraqi government, Iraq's neighbours and other stakeholders.
German Foreign Minister Frank-Walter Steinmeier summed up the reservations of several European allies when he told reporters: "A military confrontation will be only successful if it is embedded in a political setting."
Obama drew bipartisan criticism last week after saying candidly he had not yet developed a strategy for confronting the Islamic State in Syria, where militants have beheaded two U.S. journalists in the last month.
The United States acknowledged that action against IS in Iraq would have implications in Syria as well.
"We're convinced in the days ahead we have the ability to destroy ISIL. It may take a year, it may take two years, it may take three years. But we're determined," Kerry said. (Additional reporting by Kylie MacLellan, Sabine Siebold and Guy Faulconbridge. Writing by Phil Stewart. Editing by Paul Taylor/Mike Peacock)