French President Francois Hollande says the global threat posed by Islamic State (IS) militants must meet a global response.
He was opening an international summit of foreign ministers in Paris aimed at combating the jihadist group.
About 40 countries, including 10 Arab states, have signed up to a coalition to help fight IS in Iraq and Syria.
The conference follows a whirlwind tour of the Middle East by US Secretary of State John Kerry.
Mr Kerry, who is also attending the summit, has been drumming up support for a plan of action unveiled by President Barack Obama last week.
The murder of British aid worker David Haines by IS militants, shown in a video released by the group on Saturday, has added momentum to the plans, says the BBC`s Lucy Williamson in Paris.
Islamic State controls large parts of Iraq and Syria. The CIA estimates that the group could have as many as 30,000 fighters in the region.
Islamic State crisis: Hollande warns of global threat -V?DEO
15 September 2014
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