CRI听力:US Condemns British Hostage's Killing; Building Global Coalition

The United States has condemned the beheading of a Briton by Islamic State extremists, as efforts are continuing to put together a global coalition to fight the extremist group.

David Haines, an aid worker, was beheaded on Saturday, the third Westerner to be killed in this way in recent weeks.

IS militants have also threatened to kill a second Briton, 47-year-old Alan Henning.

British Prime Minister David Cameron has called Haines a "hero", while Haines's charity says the killing of vulnerable aid workers is a crime against humanity.

US officials have indicated a possible widening of the air campaign against IS, saying several Arab countries have offered to join in the fight.

Australia says it will send troops.

For the last week, Secretary of State John Kerry has travelled across the Middle East to pin down nations on what kind of support they will give to a global coalition against IS.

"The answer is yes, there are some that have said that. There are some that clearly prepared to take action in the air alongside the United States and to do air strikes, if that is what they are called on to do. What we are doing right now is putting together the whole package, and it's not appropriate to start announcing that this country will do this, this country will do that."

Kerry was speaking from Cairo where he has secured support from Egypt in the emerging coalition.

He is now in Paris, which will host international talks later today seeking a strategy against IS militants.

Nearly 40 nations have agreed to contribute to what Kerry said would be a worldwide fight to defeat the militants.