WASHINGTON - US President Barack Obama on Saturday strongly condemned "the barbaric murder" of Briton David Haines by Islamic State militants after the group released a video purporting to show the beheading of the aid worker."The United States stands shoulder to shoulder tonight with our close friend and ally in grief and resolve," Obama said in a statement. "We will work with the United Kingdom and a broad coalition of nations from the region and around the world to bring the perpetrators of this outrageous act to justice, and to degrade and destroy this threat to the people of our countries, the region and the world."Obama is calling for a coalition of Western and Middle Eastern countries to fight Islamic State. The group in the past month released videos showing the beheadings of American journalists James Foley and Steven Sotloff.