Senior figures from an emerging US-led coalition are to meet this Monday to discuss options to defeat "Islamic State" (IS) militants, with Washington keen to bring more members actively on board.

Ahead of the Paris conference, US Secretary of State John Kerry urged Washington's allies to join a united front, in particular calling upon Arab nations to play a meaningful role.

Kerry said some nations had offered to put troops on the ground and that "there are some that are clearly prepared to take action in the air alongside the United States and to do airstrikes."

"We have countries in this region, countries outside of this region, in addition to the United States, all of whom are prepared to engage in military assistance, in actual strikes if that is what it requires," Kerry told US broadcaster CBS on Sunday.

Kerry added that there was no plan to use ground troops, despite offers from some allies.

A Senior US State Department official told the Reuters news agency that offers of Arab air participation in the air campaign being carried out by IS at the behest of the Iraqi government had been made.

France to outline air contribution

France has said it is prepared to take part in US-led airstrikes on IS fighters in Iraq.

Australia, for its part, has said it us preparing to contribute 600 troops and up to 10 military aircraft to the campaign.

US President Barack Obama has also said he foresaw the training of "moderate" Syrian rebels to take on IS, as well as the reconstitution of an Iraqi army that was routed by the rapid advance of the Islamist militants across northern and western Iraq.

Monday's gathering comes amid outrage over the killing of British air worker David Haines, whose beheading has been claimed by IS fighters.

Fourth hostage threatened

Haines was beheaded by the militants in a video released on Saturday, the validity of which British officials say they have no reason to doubt. In the video, IS claims that the 44-year-old Briton was killed because of Prime Minister David Cameron's decision to join the coalition with the US and arm Kurdish Peshmerga fighters.

A hooded man in the video spoke with a British accent, as was the case in two previous videos that showed the killing of US journalists Steven Sotloff and James Foley.

IS also threatened the life of another kidnapped British aid worker it claims to be holding, 47-year-old Alan Henning.

rc/pfd (AP, AFP, dpa, Reuters)