Islamic State insurgents posted a video yesterday purportedly showing the beheading of US journalist James Foley and images of another US journalist whose life they said depended on how the United States acts in Iraq.

US President Barack Obama said yesterday the US would do what it must to protect its citizens. Photos: Reuters

The video, titled A Message To America, presented President Barack Obama with bleak options that could define America’s next phase of involvement in Iraq and the public reaction to it, potentially deepening his hand in a conflict he built much of his presidency on ending.

The video’s grisly message was unambiguous, warning of greater retaliation to come against Americans following nearly two weeks of US air strikes that have pounded militant positions and halted the advance of Islamic State, which until this month had captured a third of Iraq with little resistance.

Posted on social media, the video brought a chilling and highly personal tone to a conflict that for many Americans had started to become all too familiar.

US journalist James Foley (front centre) after being released by the Libyan government, at Rixos hotel in Tripoli, in May, 2011.

Foley, 40, was kidnapped by armed men on November 22, 2012, in northern Syria while on his way to the Turkish border, according to GlobalPost, a Boston-based online publication where Foley had worked as a freelancer. He had reported in the Middle East for five years and had been kidnapped and released in Libya.

Steven Sotloff, who appeared at the end of the video, went missing in Syria while reporting in July 2013. He has written for TIME among other news organisations. The video injected an unpredictable element into Obama’s deliberations on how far to proceed with US air strikes against Islamic State targets in Iraq, though aides said his vow not to put US combat forces on the ground in Iraq still held.

On a Facebook page for Foley, a message from his mother Diane Foley said: “We have never been prouder of our son Jim. He gave his life trying to expose the world to the suffering of the Syrian people. We implore the kidnappers to spare the lives of the remaining hostages. Like Jim, they are innocents. They have no control over American government policy in Iraq, Syria or anywhere in the world.”

The video was posted after the US resumed air strikes in Iraq this month for the first time since the end of the US occupation in 2011.

The Sunni militant group, which has declared a caliphate in parts of Iraq and Syria in areas it controls, opened the video with a clip of Obama saying he had authorised strikes in Iraq.

Situation presents Obama with bleak options about America’s next phase of involvement in Iraq

The words “Obama authorises military operations against the Islamic State effectively placing America upon a slippery slope towards a new war front against Muslims” appeared in English and Arabic on the screen.

A man identified as James Foley, his head shaven and dressed in an orange outfit similar to uniforms worn by prisoners at the US military detention camp in Guantánamo, Cuba, is seen kneeling in the desert next to a man standing, holding a knife and clad head to toe in black.

“I call on my friends, family and loved ones to rise up against my real killers, the US government, for what will happen to me is only a result of their complacency and criminality,” the man says.

Later yesterday Obama said the beheading of American journalist James Foley by Islamic State militants “shocked the conscience of the entire world” and he vowed the US would do what it must to protect its citizens.