Islamic State's beheading of a U.S. journalist and its threat to "destroy the American cross" suggests it has gained enough confidence seizing large areas of Iraq and Syria to take aim at American targets despite the risks.

On Tuesday night, Islamic State released a video of its fighters beheading James Foley, who was kidnapped in Syria nearly two years ago.

The black-clad executioner, who spoke English with a British accent, also produced another American journalist and said his fate depends on U.S. President Barack Obama's next move.