NATO-led forces are scaling back joint operations with their Afghan counterparts because of "insider attacks" which have cost the lives of 51 Western troops this year.
The International Security Assistance Force said most joint patrols and advisory work with Afghan troops would be conducted only at battalion level and above.
The BBC's defence correspondent Caroline Wyatt said that this is "a real message being sent out to the Taliban that what they are doing is working".
Colonel Tim Collins, former commanding officer in the Royal Irish Regiment, said however that he does not believe there is a Taliban strategy behind the "green on blue" attacks.
"The Taliban are taking advantage of disgruntled Afghans who have been recruited in large numbers," he told the Today programme.
"The Afghan people can look forward to a much rougher handling from their own police and army," he warned.
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