Sotloff beheading: Obama warning to Islamic State
3 September 2014 Last updated at 13:51 BST
President Barack Obama has vowed the US will not be intimidated, after Islamic State militants released a video showing the beheading of American journalist Steven Sotloff.
Mr Obama warned: "Our reach is long and justice will be served."
Another US journalist, James Foley, was similarly murdered last month.
BBC security correspondent Frank Gardner reports.