War with Isis: President Barack Obama to seek 'war powers' from Congress to confront militants

Move comes after American hostage Kayla Mueller is confirmed dead

President Obama vowed to 'bring to justice the terrorists who are responsible for Kayla's captivity and death' (Getty Images)

Even as President Barack Obama vowed to hunt down the Isis terrorists responsible for the latest killing of an American hostage, the White House was making final preparations to seek formal war powers from the US Congress to fight the group in Syria and Iraq.

Confirmation that the 26-year-old aid worker Kayla Mueller had been killed was issued simultaneously by the White House and by her family. Calling it a “hateful abhorrent terrorist group”, Mr Obama said: “No matter how long it takes, the United States will find and bring to justice the terrorists who are responsible for Kayla’s captivity and death.” He added that Ms Mueller, who was seized 18 months ago, had “epitomised all that is good in our world”.

Later, the White House said that at least one other American was being held captive. “We have avoided discussing the individual cases of Americans who have been held hostage, but we are aware of other American hostages being held in the region,” said the White House spokesman, Josh Earnest. “There have been public reports of at least one other American hostage being held in Syria.”

Exactly when Mr Obama will officially submit the Authorisation for Use of Military Force to Congress remained unclear. It will, however, be the first time that the US Congress is to consider extending new war powers to an American president in 13 years.

In an interview given to the BBC, meanwhile, the Syrian President, Bashar al-Assad, said that his regime has been receiving messages from third parties ahead of strikes carried out by the US and its allies against Isis targets in his country. “Sometimes they convey a message, a general message, but there’s nothing tactical,” he said. “There’s information, but not dialogue.” The National Security Council in Washington has insisted there has been no co-operation with the Assad regime even as his planes and those of the coalition have shared skies over Syria.

Mr Earnest said: “The US is not co-ordinating our action with the Syrian government and we are not going to.” He added that only before the start of the aerial campaign in Syria did the US government see fit to give a tip-off to Damascus via its envoy to the United Nations in New York.

For months the Pentagon has been ratcheting up air strikes over both Syria and Iraq. Some 2,700 US troops have been deployed to Iraq as advisers to help the Iraqi military repel Isis advances. But Mr Obama has thus far been forced to rely on authorisations given to his predecessor, George W Bush, in the wake of the 9/11 attacks even though the legal basis for doing so is considered flimsy.

It is partly for that reason that fresh congressional authorisation for use of force is now being sought. The White House considers it vital for the US to demonstrate fresh resolve and unity between the parties. But it will trigger debate on Capitol Hill with some members of the President’s party wary of allowing the US to get entangled in more overseas conflict.

Sources said the authorisation request will be for three years and will impose no geographical limitations on where Isis might be challenged. It is also expected to leave open the door for the possible deployment of combat forces, while making clear no extended US troop presence on the ground would be considered.

Kayla Mueller, an aid worker from Arizona, was taken hostage in Syria in August 2013 (Courtesy of the family)

Ms Mueller’s family was contacted privately by Isis over the weekend to tell them about her death, with US intelligence then confirming the details of the message.

“We are heartbroken to share that we’ve received confirmation that Kayla Jean Mueller has lost her life,” her parents, Carl and Marsha Mueller said in a statement. “Kayla dedicated the whole of her young life to helping those in need of freedom, justice and peace.”

The Pentagon made clear who it believes killed her. Navy Rear Adm. John Kirby was asked if there was any doubt who was responsible. He replied: “No doubt. Isil [Isis].” Kirby said officials still don’t know how Mueller died. But he added that it was not in a Jordanian air strike.

The White House is also taking steps to create for the first time an agency to gather intelligence about cyber security. Officials said it would be modelled on the National Counterterrorism Centre set up in the aftermath of the 2001 terror attacks.