NATO advisers want Afghan soldiers to spend less time manning checkpoints and more taking the fight to Taliban militants, a key tactical shift the coalition hopes will enable local forces to quell a rising insurgency.

With NATO's combat mission officially over, and only a few thousand foreign troops left, the onus has fallen on the Afghan army and police to impose stability, and the military alliance is looking for ways to use those resources more effectively.

Reducing reliance on thousands of poorly defended checkpoints that dot towns and roads across the country is a priority for NATO heading into summer, when fighting is expected to intensify as the Taliban renews its push to seize back power.

"They've got way too many soldiers on checkpoints," said Brigadier-General Wilson Shoffner, spokesman for the NATO-led training mission known as Resolute Support.

"There's an old military saying that if you defend everywhere you defend nowhere, and it's very much true for them (Afghan security forces)."

There are early signs the idea is catching on.

Over the past week, army units in the embattled province of Helmand abandoned their outposts in several of the most disputed areas, a move officials said would allow them to consolidate forces for renewed attacks on insurgent strongholds.

"We have decided to pull out our troops from their defensive role and prepare them for an aggressive role in the coming year," said General Murad Ali Murad, commander of the Afghan army's ground forces.

"We are providing them with serious training and better equipment in order to prepare for a spring offensive."

But countrywide, obstacles remain to changing tactics long favoured by security forces.

Despite providing the enemy with an obvious target, checkpoints are still simpler to defend than launching mobile operations, which require logistics and air support often beyond the reach of limited Afghan resources.

Politics can also complicate efforts to change strategy, Shoffner said.

"If you're a local chief of police or village elder, you want as many checkpoints as you can get around your village. So we often have conflict between the Afghan army that is trying to reduce checkpoints and the (local) leaders ... that want them."

"CHECKPOINTS STOP THE TALIBAN"

South of Kabul, members of the Afghan National Army's 1st battalion, 111th Capital Division hold a string of checkpoints to secure the mountain passes between the Afghan capital and Logar province.

Of roughly 600 soldiers in the battalion, more than 500 are based at checkpoints, while a small, more heavily armed mobile reserve force remains at a central base, said battalion commander Lieutenant Colonel Mohammed Reya Khuram.

"We have to have checkpoints to stop the Taliban," Khuram told Reuters. "If we are not there, the Taliban will be."

The outposts range from small earthen forts strung with barbed wire, to makeshift dugouts and shacks perched on rocky slopes. Many have no vehicles of their own, limiting troops' ability to venture far without help from the central base.

While the area is not among the most violent in the country, soldiers say they are regularly targeted by Taliban snipers and find roadside bombs.

The Defence Ministry referred Reuters' requests for comment for this article to Major General Abdul Nasir Ziaee, 111th Division commander. He said checkpoints were not necessarily wrong.

"We have two groups of soldiers at each checkpost. One is the security group and another is the reaction group," he said. "The security group patrols and the other one responds to attacks, or when they get a report they react."

But recent examples underline the risk of relying on static defences.

This month, insurgents used captured military vehicles to attack a checkpoint in Helmand, southern Afghanistan, killing seven soldiers and 15 policemen.

In the east, checkpoints were among the first targets for militants supporting Islamic State when they attacked last year.

When troops fail to leave forts to conduct patrols and operations, it allows insurgents to place roadside bombs and mines, further restricting the military's ability to move, according to coalition officers.

Western officials privately estimate the Taliban are contesting as much territory as at any time since their regime was toppled in 2001, underlining the need to wrest back the initiative.

Government forces, numbering more than 300,000 including soldiers and police, are only fully in charge of about 70 percent of the country, the U.S. military says.

Outposts can be a key part of disrupting insurgent movement, NATO military officers say, and during more than a decade of combat operations the coalition itself fought fiercely to establish small bases in Taliban strongholds in eastern and southern Afghanistan.

But fewer, stronger outposts can be an advantage, Shoffner argued.

"The idea is to reduce checkpoints and to consolidate onto strong points, so that not only does that strong point have the strength to defend itself, but so it also has a manoeuvre capability," Shoffner said.

"So if there is a security situation in a nearby village or checkpoint, it's got enough combat power to overwhelm whatever the security threat is."