US Secretary of State John Kerry will meet foreign ministers from around the world in Paris on Monday to discuss how to defeat Islamic State (IS) militants.
French President Francois Hollande said the beheading of a British aid worker showed the world must act against IS.
About 40 countries, including 10 Arab states, have signed up to a coalition to help fight IS in Iraq and Syria.
Several Arab countries have offered to take part in air strikes on IS fighters in Iraq, US officials say.
Mr Kerry says he is “extremely encouraged” by promises of military assistance to tackle the militant group.
He spoke after a whirlwind tour of the Middle East to try to drum up support for a plan of action unveiled by US President Barack Obama last week.
The US strategy to weaken the group centres around 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, will focus on how these plans can be put into place.
It is being co-hosted by Iraqi President Fouad Massoum.
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 expected to attend.
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, who said President Obama’s plans would fail without involving Iraq’s neighbour.
“Syria fought against terrorism and we shall be in the centre of any real and serious battle against terrorists,” Syria’s Deputy Foreign Minister, Faisal Mekdad, told the BBC.
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.