LONDON (AFP) - Britain joined the United States on the frontline against the Islamic State in Iraq and Syria (ISIS) on Wednesday after a British hostage's life was threatened in a gruesome video, with London saying it would not rule out taking part in air strikes if necessary.
"I can assure you that we will look at every possible option to protect this person," Foreign Secretary Philip Hammond said after an emergency government meeting held on the eve of a two-day summit of NATO leaders in Wales.
Cameron chaired the meeting, which was called after the release on Tuesday of a video showing the execution of a second US journalist by Islamist fighters in Iraq.
"A country like ours will not be cowed," Cameron said, adding: "We will not waver in our aim of defeating terrorism".
In a video showing the severed head of 31-year-old Steven Sotloff, a masked militant warned that a British man, widely identified as David Cawthorne Haines, would be killed in response to US air strikes against militants in northern Iraq. Britain and the US have both authenticated the recording.
The militant spoke English with a British accent similar to that of the alleged killer of journalist James Foley in a video released by ISIS extremists last month.
"We will look very carefully at the options available to us to support the legitimate government of Iraq and Kurdistan in defending themselves," Hammond said. "If we judge that air strikes could be beneficial, could be the best way to do that, then we will certainly consider them but we have made no decision to do so at the moment.
"We have to deal with ISIS on the basis of the wider threat that they pose to the British public as well as this individual," he said.Speaking on Tuesday, Cameron condemned Sotloff's beheading as "a despicable and barbaric murder".
"ISIL (ISIS) terrorists speak for no religion," Cameron said, using another acronym for the terror group. "The only way to defeat it is to stand firm and to send a very straightforward message - a country like ours will not be cowed by these barbaric killers.
"If they think that we will weaken in the face of their threats, they are wrong. It will have the opposite effect. We will be more forthright in the defence of the values - liberty under the rule of law, freedom, democracy - that we hold dear, and I'm sure a united message to that effect will go forward from this House today," he told parliament.
Britain has so far not joined in US air strikes against the Islamist fighters, but has helped arm Kurds fighting in northern Iraq and has dropped aid to people surrounded by ISIS fighters on Mount Sinjar and in the town of Amerli.
Earlier this week, however, Cameron implied he could order air strikes without prior approval from parliament - something the government failed to get last year when it was considering retaliation for the use of chemical weapons in Syria. Cameron said he would keep parliament "permanently updated".
"If, however, something needed to be done urgently to protect a particular British national interest or to prevent some humanitarian catastrophe, it might be necessary to act and then come to parliament," he said on Monday.
"We have to make a judgment about how we best help those on the ground, and to date that judgment has been to provide aid and political support and to help with certain military aspects.
"The Americans have gone further and provided air strikes," Cameron said. "I think that is the right way to approach this problem."