Supplies for NATO in Afghanistan have been hit by a Pakistani blockade enforced after a cross-border strike killed 24 of its troops, but it remains unclear how seriously coalition forces will suffer.

There are around 140,000 foreign troops in landlocked Afghanistan waging a 10-year battle against a Taliban-led insurgency who rely on fuel, food and equipment brought in from outside.

Nearly half of all cargo bound for foreign troops routes through Pakistan, which closed the border to NATO traffic on Saturday. But the coalition force insists its fight against the Taliban will not be affected.

"ISAF uses a vast supply and distribution network to ensure coalition forces remain well-stocked in order to carry out their assigned mission across Afghanistan," said Lieutenant Gregory Keeley, a spokesman for the NATO-led International Security Assistance Force (ISAF) in Kabul.

Some 48 percent of all coalition cargo usually passes through two points on the Pakistan border, while for US forces, who provide around 100,000 troops in Afghanistan, the figure is around 30 percent, he said.

ISAF and the US have been building up alternative supply routes through Turkmenistan, Uzbekistan and Tajikistan from the north of Afghanistan as relations between Washington and Islamabad have deteriorated this year.

The so-called Northern Distribution Network has been built up to address concerns about over-reliance on Pakistani supply lines amid what was a growing US troop commitment in Afghanistan.

The northern route accounts for 52 percent of coalition cargo transport and 40 percent for the US, which also receives around 30 percent of its supplies by air, Keely said.

But US officials admit that the Pakistan route is cheaper and shorter.

John Bolton, former US ambassador to the United Nations, told Fox News that US forces also keep stockpiles in case supply lines are choked as in the past.

"This is not the first time, our forces do have stockpiles on the Afghan side of the border," he said. "It is obviously something that needs to be corrected but there is no immediate concern."

Keeley would not discuss how long stockpiles would tide foreign troops over, calling it an "operational issue."

The last time the Pakistani border was closed to foreign military supplies was in September last year for 10 days following a previous NATO strike that killed up to three Pakistani soldiers.

The deadliest such incident prior to the weekend strike came in June 2008 when another NATO strike killed 11 Pakistani soldiers.

Some warn that ISAF will need to take swift action to address Saturday's murky incident to ensure that supplies are not disrupted in the longer-term.

"Even a closure lasting more than a week should not impact operations on the ground, especially now that stockpiles have been established and the alternative Northern Distribution Network has been significantly expanded," intelligence analysts Stratfor wrote in assessment of the situation.

"But Washington is not yet completely free of its reliance on supplies moved through Pakistan and so will need to find a way to resume the flow."

Retired US general Barry McCaffrey told NBC News that he believed the coalition effort in Afghanistan was "one step short of a strategic crisis."

"I do not believe we can continue operations at this rate," he said. "So we've got to talk to them, we've got to pay them, we've got to apologise for this strike. We have no option, literally."