"The United States strongly condemns the brutal murder of United Kingdom citizen Alan Henning by the terrorist group ISIL," Obama said yesterday.
Henning worked to help improve the lives of the Syrian people and his death is a great loss for them, for his family and the people of the UK, he said.
"Standing together with our UK friends and allies, we will work to bring the perpetrators of Alan's murder as well as the murders of Jim Foley, Steven Sotloff and David Haines to justice," he added.
"Standing together with a broad coalition of allies and partners, we will continue taking decisive action to degrade and ultimately destroy ISIL," Obama said.
The 47-year-old from Manchester in northwest England had volunteered to help drive an aid convoy to Syria for a Muslim charity, and was kidnapped 10 months ago.
This is the fourth such video released by the Islamic State group.