An international summit of foreign ministers is taking place in Paris to discuss a strategy to combat the Islamist State (IS) militant group.
About 40 countries, including 10 Arab states, have signed up to a coalition to help fight IS in Iraq and Syria.
Opening the talks, French President Francois Hollande said the threat was global and the response must be global.
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.
Iraqi President Fuad Masum, who is co-hosting the conference, said the international community must pursue the jihadists wherever they are.
In his opening remarks, Mr Hollande called for the complete support of moderate rebels in Syria.
"Chaos plays into the terrorist's hands," he said.
"Therefore we have to support those who are able to negotiate and make the necessary compromise in order to preserve the future of Syria, and for France those are the forces of the democratic opposition."
Earlier, France said it had begun surveillance flights over Iraq.
"This very morning, the first reconnaissance flights will be carried out in agreement with the Iraqi and Emirati authorities," Defence Minister Jean-Yves Le Drian told French troops on Monday at the Al-Dhafra base in the United Arab Emirates.
Britain revealed in August that Tornado jets and surveillance aircraft were involved in intelligence gathering over Iraq.
Several Arab countries have offered to take part in air strikes on IS fighters in Iraq, US officials say.
Turkey, however, will only allow humanitarian and logistical operations from the Nato air base on its soil.
Mr Kerry said he was "extremely encouraged" by promises of military assistance to tackle the militant group.
The US strategy to weaken the group centres on military support for Iraq but also includes plans to stop foreign fighters from joining the group, cutting its funding streams and trying to counter its ideology.
The Paris conference, which will be attended by UK Foreign Secretary Philip Hammond among others, is aimed at defining the role each member state will play in the fight to destroy IS.
Representatives from the 10 Arab states who are part of the coalition - Egypt, Iraq, Jordan, Lebanon, Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates - are believed to be attending.
Iran dismissed the talks as "just for show" after voicing its unhappiness at not being on the "selective guest list".
The US-led coalition also came under fire from Syria, which said President Obama's plans would fail without involving Iraq's neighbour.
The brutal murder of British hostage David Haines by IS militants, shown in a video released by the group on Saturday, has added momentum to the plans being discussed in Paris, says the BBC's Lucy Williamson.
In a statement on Sunday, the UN Security Council condemned the murder as "heinous and cowardly" and said that IS "must be defeated".
Australia announced at the weekend that it was sending 600 troops and up to eight fighter jets to the UAE ahead of possible combat operations in Iraq.
However, Mr Kerry told US broadcaster CBS that the US was not seeking troops on the ground at the moment.
Islamic State controls large parts of Iraq and Syria and the CIA estimates that the group could have as many as 30,000 fighters in the region.
Since August, US fighter jets have conducted about 160 air strikes on IS positions in Iraq.
Credit: The BBC
