The fight against Islamic State militants could last another 15 years, according to a former British diplomat in the Middle East.
Sir John Jenkins, who retired as the UK's ambassador to Saudi Arabia this year, warned the threat IS posed was potentially the gravest situation the region faced since the end of WWII.
His comments came as David Cameron said the challenge of Islamist extremism would take "years rather than months" to address.
Sir John, who also served in Iraq, Syria, Libya and Israel during his Foreign Office career, said: "This is probably the most challenging set of circumstances countries in the region, particularly in the Gulf, have faced since the 1960s and maybe since the end of the Second World War."
"I wouldn't be surprised if we were looking at 10 to 15 years of instability and insecurity in Iraq, in Syria, in parts of north Africa."
MPs called for the UK to step up its involvement after a report found Britain is playing a lesser role than other countries and does not have a clear strategy for defeating the terror group.
Barack Obama is expected to ask congress to authorise the US military to use more force against Islamic State (IS) militants.
The President has been relying on congressional authorisations that President George W Bush used to justify action after 9/11.
He has been ordering airstrikes in Iraq and Syria for months but further details are being worked out over what America's next move is.
Republican House Speaker John Boehner said: "The president believes it sends a very powerful signal to the American people, to our allies, and even to our enemies, that the United States of America is united behind this strategy to degrade and ultimately destroy IS."
However, Mr Earnest declined to discuss specific provisions being discussed, such as how long the authorisation will last, what geographical areas it will cover and whether it will allow for the possibility of ground troops.
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Britain should step up its military response to help in the battle against Islamic State militants, a committee of MPs has said.
The Defence Select Committee (DAC) said the UK's involvement to date had been "strikingly modest".
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A report found Britain is playing a lesser role than other countries and does not have a clear strategy for defeating the terror group.Read the full story ›
Families who lost loved ones in the Iraq war feel ignored by the Chilcot Inquiry one mother has told ITV News.
Rose Gentle, whose son Gordon was killed in Iraq more than ten years ago, said: "I don't think a lot of them are actually thinking of the families, not just the Chilcot Inquiry. I think a lot of these people holding back documents are not even giving the families a second thought."
The head of the inquiry into the Iraq war is to face MPs today to explain the delays in the final report, more than five years after the probe was launched.
Sir John Chilcot will face questions from MPs amid fierce criticism of the delays.
The inquiry chairman will appear before the Foreign Affairs Committee to discuss the process and "obstacles which remain". Prime Minister David Cameron has been among those expressing frustration that the report has yet to be finalised.
America and its allies carried out 27 air strikes against Islamic State militants in Iraq and Syria since early Friday, the Combined Joint Task Force leading the operation reported.
Ten of the 17 strikes in Iraq hit near the oil city of Kirkuk, it said. In Syria, Islamic State targets near the border town of Kobani were attacked in eight of the 10 raids, the statement said.
The death of an Islamic State chemical weapons expert is expected to temporarily "degrade and disrupt" their use against "innocent people" US Central Command said in a statement.
His death is expected to temporarily degrade and disrupt the terrorist network and diminish ISIL's ability to potentially produce and use chemical weapons against innocent people.
US Central Command has issued a statement saying Islamic State chemical weapons expert Abu Malik, was killed in a coalition airstrike on January 24 near Mosul, Iraq.
Malik had been a chemical weapons engineer during the rule of Saddam Hussein and then affiliated himself with al Qaeda Iraq in 2005, Central Command said.
When he joined Islamic State, also known as ISIL, it gave the insurgent force a chemical weapons capability, the statement said.