ISLAMABAD, Pakistan (CNN) -- Pakistan has indefinitely blocked travel for convoys, carrying food and military supplies to U.S. troops in Afghanistan, through a key mountain pass.

Armed militants pose next to a captured armored vehicle near the Pakistan-Afghanistan border.

But in a statement, the NATO-led International Security Assistance Force in Afghanistan said, "We do not expect any impact on ISAF's ability to carry out operations."

The decision to suspend travel through the Khyber Pass in northwest Pakistan was taken due to security concerns, said Gula Jan, a security official in Khyber Agency, on Sunday.

The mountain pass links Pakistan to its neighbor, Afghanistan. It is in the Khyber Agency, one of seven semiautonomous tribal agencies along the Afghan border.

Because Afghanistan is landlocked, many supplies for NATO-led troops fighting Islamic militants there have to be trucked in from Pakistan. Officials said militants aligned with the Taliban and al Qaeda have carried several attacks there.

The Pakistani central government has little control in the area, and the area is believed to be a haven for militants.

On Tuesday, as many as 60 to 70 armed militants launched back-to-back assaults on convoys.

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The militants seized 13 trucks -- 12 carrying wheat into Afghanistan as part of a World Food Programme convoy, and one transporting Humvees to the U.S.-led coalition, Khyber Agency officials said.

Jan said the decision to suspend travel came after local leaders met with representatives of some of the shipping firms. He said trucks will be allowed through the pass once the security situation improves, but did not specify a date.

Dozens of trucks idled by the side of roads Sunday in the Khyber Agency and in Peshawar waiting for the green light.

In its statement, ISAF said it has "multiple, robust and complementary lines of support."

It added that for security and geographical reasons, "the movements of civilian convoys destined for ISAF are coordinated with Pakistani authorities and border crossing points. The current temporary adjustments in convoy movements are as a result of this coordination."

CNN's Reza Sayah contributed to this report.

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