Foreign Secretary David Miliband will call on the Afghan government to put more effort into the pursuit of a political solution to end fighting.

Mr Miliband will say a political settlement involving dialogue with the Taliban is just as important as the military effort.

And he will blame corruption in Afghan politics for motivating the insurgency.

In a lecture at the Massachusetts Institute of Technology in the US, Mr Miliband will say: "My argument is that now is the time for the Afghans to pursue a political settlement with as much vigour and energy as we are pursuing the military and civilian effort.

"The political settlement needs to be external as well as internal, involving all of Afghanistan's neighbours as well as those parts of the insurgency willing permanently to sever ties with al Qaida, give up their armed struggle and live within the Afghan constitutional framework."

Mr Miliband's Compton lecture comes as the death toll for British service personnel in Afghanistan continues to mount.

On Tuesday, the Ministry of Defence named two more soldiers - Corporal Stephen Thompson, 31, from 1st Battalion The Rifles, and Lance Corporal Tom Keogh, 24, from 4th Battalion The Rifles - killed in Helmand province.

There are fears that a lack of planning in Kabul could effectively prolong the war.

Mr Miliband, a Kennedy Scholarship student at MIT in 1988, will say a lack of security in Afghanistan and Pakistan means those two countries now "represent the number one national security threat to the UK".

He will also echo Prime Minister Gordon Brown, President Barack Obama, and Isaf commander General Stanley McChrystal, by calling for a political push.