John Hutton: Fundamental extremism is "a risk to our country"
Defence Secretary John Hutton has said the Afghanistan war is a "fundamentally important" one which will "define much of the politics of the 21st century".
He said Nato's European members must do more if it was to "come through this test of its resolve and character".
Lessons learned there and in Iraq would lead to a "transformation" of policy by the UK Ministry of Defence.
He also told the BBC troops could leave when Afghan forces could "manage the insurgency at an appropriate level".
Mr Hutton sought to set out the goals of the mission in interviews for BBC One's Politics Show and BBC Radio 4's the World this Weekend ahead of meeting his US counterpart this week.
He said UK troops, whom he paid tribute to, were in Afghanistan "first and foremost to tackle fundamental extremism which is a risk to the security of our citizens and our country".
Troops were doing that by trying to protect the local population from the influence of those extremists, he added. They were also seeking to build up credible and determined Afghan security forces.
In the process, he said, this would allow Afghan politicians to "create more of a consensus for people to come together and put down their weapons".
We do face a very significant international threat to our way of life, our values - maybe not our borders but our values, from international terrorism
John Hutton UK defence secretary
Asked if the Taleban could be beaten militarily, Mr Hutton said: "The Taleban can't beat us. They don't pose a tactical or strategic threat to Nato and Isaf forces.
"What we've got to concentrate on is protecting the local population from the extremists and the terrorists and build up these credible Afghan forces.
"Because the one thing that will allow us to come out of Afghanistan at some point is when we can leave behind credible and determined security forces who can manage the level of insurgency at an appropriate level.
"Now we are some distance away from that at the moment. We can stop them (the Taleban) taking control of the country... I do believe that with our Afghan partners we can succeed in Afghanistan and secure Afghan democracy and give Afghan citizens the chance to live their life in peace and security."
Asked if the mission had changed to a counter-insurgency one, Mr Hutton said lessons had to be learned from the "complicated operations" in Iraq and Afghanistan as they were going to "define the characteristics of future conflict for decades" and "much of the politics of the 21st Century".
Mr Hutton said the Ministry of Defence was going to "focus very heavily" over the next year on changes to training and equipment.
Asked if he was describing a "policy transformation" Mr Hutton said: "Yes. And I think this is going to affect the armed forces of all of the Nato countries.
"This is the challenge for our generation and it's a good thing in a sense. We don't run the risk of inter-state warfare threatening European homeland security but we do face a very significant international threat to our way of life, our values - maybe not our borders but our values, from international terrorism.
"So we've all got to be part of this learning exercise in Nato, all the way through the alliance, we've all got to learn the lessons of the last few years."
He also said that European members of Nato had to do more and not expect the US to do all the "heavy lifting".
The defence secretary's comments come the day after a soldier from the 2nd Battalion, Royal Welsh Regiment was killed in an explosion in Musa Qala in northern Helmand.
He has been named as Lance Corporal Christopher Harkett, 22, from The 2nd Battalion, Royal Welsh Regiment.
His death brings the number of British service personnel killed in Afghanistan since operations began in 2001 to 150.
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