NATO has already handed over the relatively peaceful province of Bamiyan and the eastern town of Mehter Lam.

Maintaining stability in Lashkar Gah will be the sternest test yet for local forces.

The handover is seen as a critical step in a transition of power before foreign troops end combat operations in 2014.

NATO handed over responsibility for the security of Mehter Lam, the capital of eastern Laghman province, on July 19. Mehter Lam is considered to be a relatively secure city, but there were reports of a mortar attack near the city during the handover ceremony.

Seven areas were designated to be passed to local forces under a plan announced by President Hamid Karzai in March. The remaining four areas to be handed over are: Kabul province, Panjshir province, Herat city and Mazar-e Sharif city.

Observers agree that the greatest challenge for Afghan forces is likely to be faced in Lashkar Gah, the capital of Helmand province, where Taliban insurgents remain active.

On July 18, seven policemen were killed at a checkpoint near the city, just outside the area due to be handed over. And on July 16 a British soldier was killed while on a routine patrol in the area - some reports suggest he was shot by a man in an Afghan army uniform.