Afghan district police chief Ahmadullah Anwari only has enough grenades to hand out three to each checkpoint in an area of Helmand province swarming with Taliban insurgents who launch almost daily attacks on security forces.

"Sometimes up to 200 Taliban attack our checkpoints and if there are no army reinforcements, we lose the fight," said Anwari, in charge of one of Afghanistan's most volatile districts, Sangin.

"It shames me to say that we don't have enough weapons and equipment. But this is a bitter reality."

As most foreign combat troops prepare to leave Afghanistan by the end of 2014 after 13 years of war, the experiences of Anwari and other police chiefs and army commanders across the country are NATO's biggest worry.

The United States, which provides the bulk of NATO troops in Afghanistan, has poured some $61 billion into training a nascent 350,000-strong security force, seeing it as the lynchpin of a plan to exit its longest war.

U.S. and Afghan commanders have praised the bravery and effectiveness of local soldiers, police and others in the face of a Taliban onslaught that has killed more than 4,600 Afghan security force members already this year.

And, despite increasingly deadly suicide bombings and assaults on military and civilian targets, most of the country is under government control, albeit loosely in some areas.

"The Afghan national security forces are winning, and this is a hugely capable fighting force who have been holding their ground against the enemy," Lt. Gen. Joseph Anderson, second-in-command for coalition forces, told a recent press briefing.

Yet wary of the threat posed by the Taliban as thousands of troops, and most of their sophisticated arms and equipment, head for the exit, Washington appears to be hedging its bets.

President Barack Obama recently freed those few thousand U.S. soldiers remaining post-2014 as part of a 12,000-strong NATO force to engage the Taliban in combat if necessary.