A senior US military analyst says any military strategy in Afghanistan will be futile if the US fails to provide decisive leadership.

In an interview with Al Jazeera's Shihab Rattansi, Anthony Cordesman, an adviser to General Stanley McCrystal, the new Nato commander in Afghanistan, warned against the continuation of what he called "half-measures" in Afghanistan.

Cordesman said such measures allow the Taliban to continue taking the initiative and win what he called "a battle of political attrition".

But he said the US must also have an exit strategy with a firm destination, and must be prepared to re-establish a new form of security structure.