Several Arab countries have offered to launch air attacks on the group calling itself the Islamic State, US officials said, suggesting a widening of Washington's campaign against the group.

The officials declined to identify which countries made the offers, but said on Sunday they were under consideration as the US begins to identify roles in its coalition against fighters who control parts of Iraq and Syria.

"I don't want to leave you with the impression that these Arab members haven't offered to do air strikes because several of them have," a senior US State Department official said in Paris.

The officials who would not be named, added that the offers were not limited to targets in Iraq. US President Barack Obama last week said that the US would widen its campaign, which has been restricted to Iraq.

On Thursday US Secretary of State John Kerry won backing for a "coordinated military campaign" from 10 Arab countries including, Egypt, Iraq, Jordan, Lebanon, and six Gulf states including Saudi Arabia and Qatar.

So far, France has been the only country to publicly offer to join US air attacks on Islamic State targets, although it has said its involvement would be limited to Iraq.

The US comments come a day after the IS group stirred fresh outrage with release of a video of the beheading of British aid worker David Haines.

British Prime Minister David Cameron called it "a despicable and appalling murder", and vowed to bring the killers to justice.

Participants of the US coalition against the fighters will meet for talks on Iraq in Paris on Monday.

The conference brings Iraqi authorities together with 15 to 20 international players.

It comes ahead of a UN Security Council ministerial meeting on September 19 and heads of state meeting at the UN General Assembly later this month.

As of Saturday, US fighter jets had conducted 160 air strikes on Islamic State positions in Iraq.