Islamic State: Barack Obama to lay out US plan to 'degrade and destroy' Isis in key speech

The President is expected to call for wider American intervention in Iraq

Barack Obama will not want to ally himself with President Assad (AP)

Barack Obama is expected to ask Congress for permission to arm Syrian opposition forces when he outlines America’s strategy against the Islamic State (Isis) tonight.

The US President is delivering a key speech from the White House at 9pm local time (2am BST) to back up his vow to “degrade and destroy” the militant group that has beheaded two American journalists and killed thousands in its bloody sweep across Syria and Iraq.

That the speech will be broadcast across US television networks is a sign of its seriousness, as the Government rarely interrupts prime American show times.

Officials believe Mr Obama will press forward with wide-ranging air strikes against Isis in Iraq, increasing support for the Iraqi security forces and working in coalition with European counties and partners in the Middle East.

The White House said he would welcome action from Congress but “has the authority he needs” to take action.

Increased intervention in the Middle East is at odds with Mr Obama’s election pledge to end the war in Iraq and his speech on Wednesday will come hours before the commemorations for the 9/11 terrorist attacks in New York.

He is expected to seek authorisation from Congress to arm the moderate Syrian opposition, who are fighting President Bashar al-Assad’s regime as well as Isis, after a $500 million (£310 million) programme stalled earlier this year.

Mr Obama has repeatedly ruled out sending ground troops so is likely to move towards CIA-backed training camps and increased air strikes, which have so far been limited to protecting American interests and humanitarian missions.

At a private dinner Monday with foreign policy experts, he emphasised the importance of viewing the Islamic State as one organisation, not two groups separated by the Iraq-Syria border.

In a shift for a country weary, like Britain, of interventionist wars, new polls suggest the American people would support a sustained air campaign, including extending operations into Syria.

Unlike in Iraq, the US would not be acting at the invitation of a host government but some international legal experts claim attacks could be justified as a matter of self-defence.

Mr Obama has vowed that “justice will be served” for the Isis terrorists who decapitated American journalists James Foley and Steven Sotloff, and threatened another British hostage’s life.

“Whatever these murderers think they will achieve by killing innocent Americans like Steven, they have already failed,” he said.

“The bottom line is this: our objective is clear and that is to degrade and destroy (Isis) so that it’s no longer a threat not just to Iraq but also the region and to the United States.

"Those who make the mistake of harming Americans will learn that we will not forget, that our reach is long and that justice will be served."

The rhetoric in Britain has been less strong, with David Cameron emphasising the need to tackle the cause of extremism and reconcile religious and ethnic tensions between Sunnis and Shias in Iraq.

At the end of the Nato summit in Wales, where member countries discussed Isis as well as Ukraine and other conflicts, he said: “We will continue to encourage countries in the region to support this effort and we’ll continue to work with our partners on the ground to take all necessary steps to squeeze this barbaric terrorist organisation out of existence.”

Additional reporting by AP