"As Nato withdraws forces and reduces its presence in Afghanistan, the Taliban are going to change their tactics," he told the BBC. "They're going to modify their strategy and they are going to do more and more spectacular attacks."
"A lot of Western analysts now say al Qaida's main base is no longer Afghanistan - it's maybe Mali, it's maybe Somalia, it's maybe North Africa," he said.
"Or maybe it's a sleeping cell in some corner of Europe, so why should we have massive force here?
"But if Afghanistan remains unresolved... it means an ally of al Qaida re-dominating the country, whether partly or wholly. The current effort to under-estimate the strength of the Taliban, to try to de-link them from al Qaida in our own imaginations is wrong."
He said that ultimately the key to resolving the problems of Afghanistan lay in neighbouring Pakistan.
"It is executed by al Qaida, by Taliban, but the hub of this militant extremism is Pakistan," he said.
"I am reminded time and again that your days are numbered and (you) are leaving. We didn't bring you here. If the West does not solve the problem of Pakistan, you will regret it one day."