Britain has resisted calls to join a US coalition to launch airstrikes against the Islamic State, even in the hours after the terror group released a gruesome video showing the beheading of UK citizen David Haines.

The US State Department confirmed Sunday that several Arab nations had moved to join the US air campaign against the militants, but British Prime Minister David Cameron remained cautious in his statement condemning the Haines execution.

While Cameron promised to "drive back, dismantle, and ultimately destroy ISIL and what it stands for," in a televised statement from Downing Street on Sunday, he also said that Britain would "do so in a calm, deliberate way."

In his address, Cameron also hailed Haines, a 44-year-old aid worker and father of two, as a "hero," saying, "We will hunt down those responsible and bring them to justice, no matter how long it takes."

The murder of David Haines is an act of pure evil. My heart goes out to his family who have shown extraordinary courage and fortitude. — David Cameron (@David_Cameron)September 13, 2014

The footage released Saturday purportedly shows the execution of Haines and is consistent with a recent series of beheadings perpetrated by the Islamic State. The Haines execution tape, titled "A message to the Allies of America," features him kneeling in front of his captor and blaming Cameron for his death.

"I would like to declare that I hold you, David Cameron, entirely responsible for my execution," Haines says in the video. "You entered voluntarily into a coalition with the United States against the Islamic State, just as your predecessor, Tony Blair, did. Following a trend amongst our British Prime Ministers who can't find the courage to say no to the Americans.

"Unfortunately, it is we, the British public, that in the end will pay the price for our Parliaments selfish decisions."

Haines previously appeared toward the end of the execution tape of American journalist, Steven Sotloff, nearly two weeks ago. Haines was threatened then with death if Britain and US allies did not cease their military assault against the IS.

The format of the tape also closely resembles the earlier execution video of another American journalist, James Foley, released August 19.

The unidentified executioner in each of the videos also appears to be the same masked captor who speaks with a London accent and has been dubbed by British media as "Jihadi John."

Yet despite Haines' reference to Britain's engagement with the US, or perhaps because of it, Cameron today once again shied away from banding with American allies in launching airstrikes against the militants in Syria.

Before any sort of air campaign can be approved, Cameron would first need to reconvene parliament, currently in recess, and he has so far made no moves to do so. Lawmakers previously rejected the prime minister's proposed airstrikes in Syria last year.

President Obama outlined his long-awaited strategy to "degrade and ultimately destroy" the Islamic State on Wednesday. The plan involves airstrikes in Iraq and Syria, and the deployment of additional military advisors who would be there in a strictly non-combative capacity.

A host of Middle east allies including Egypt, Iraq, Lebanon, Jordan, Qatar, and Saudi Arabia, all officially pledged to support Obama's strategy the day after the plan was announced.

On Sunday, the State Department announced it was considering several offers from unspecified Arab nations to join in air strikes against the IS targets in Iraq and "elsewhere," according to Reuters.

Cameron said he had not ruled out any options against the militants — save for a ground force incursion — but with his priorities directed toward more immediate domestic issues, such as the upcoming Scottish referendum for independence, decisive military action abroad may not be forthcoming.

Britain's involvement in countering the IS insurgency has been limited to contributing humanitarian aid, providing arms and possible training to Kurdish fighters battling the IS in Iraq, and carrying out surveillance.