Washington (AFP) – The U.S. military suspended shipments of equipment out of Afghanistan through Pakistan, citing protests that posed a risk to truck drivers, officials said.

The move came after club-wielding activists in northwest Pakistan forcibly searched trucks for NATO supplies in protest over U.S. drone strikes in the tribal belt.

“We have voluntarily halted U.S. shipments of retrograde cargo through the Pakistan Ground Line of Communication (GLOCC) from Torkham Gate through Karachi,” said Pentagon spokesman Mark Wright in a statement.

Wright was referring to the main overland route used by the Americans and NATO to withdraw military hardware from Afghanistan, as part of a troop pullout set to wrap up by the end of 2014.

The delay in removing the equipment is just the latest hitch in a deeply troubled relationship between Pakistan and the United States.

Relations have been particularly fraught since CIA drone missile attacks in Pakistan which have raised tensions with Islamabad and sparked public outrage.

US officials said trucks have been told to wait for now in holding areas in Afghanistan.

“We anticipate that we will be able to resume our shipments through this route in the near future,” Wright said.

A defense official said Washington believed the Islamabad government fully supported the use of the route and that it would soon restore security to the area.

“The companies that we contract with were getting nervous. And it’s getting a little too dangerous for the truck drivers,” the defense official, who spoke on condition of anonymity, told AFP.

The United States has alternative routes available to the north through Central Asia, though those options take longer and are more expensive.

“While we favor shipping cargo via Pakistan because of cost, we have built flexibility and redundancy into our overall system of air, sea and ground routes to transport cargo into and out of Afghanistan,” Wright said.

The U.S. and Pakistani governments recently issued a joint statement saying the road route through Pakistan was considered important to both Washington and Islamabad, as well as the NATO alliance, he added.

About half of U.S. cargo is being taken out through the Pakistan route via the Torkham crossing, with the remainder being removed by aircraft or a combination of planes and then ships at regional ports.

NATO cargo shipments across Pakistan have been disrupted in the past due to political strains.

Islamabad shut its border to coalition trucks for more than seven months after a U.S. helicopter accidentally killed 24 Pakistani troops.

The border reopened to supply trucks in July 2012 after Washington issued an apology.

As of September, the Pentagon said it had to send home 24,000 vehicles and 20,000 shipping containers of equipment after more than 12 years of war.

The Pentagon flies out weapons and other sensitive gear.

The whole withdrawal will cost an estimated $7 billion, according to Pentagon officials.

U.S. officials say the drone strikes by unmanned aircraft have taken out dangerous Al-Qaeda militants.

While Pakistani officials publicly criticize the bombing campaign, the government is believed to have tacitly backed at least some of the strikes over the years.

Civilian deaths from America’s covert drone operation have also proved contentious in Afghanistan, where President Hamid Karzai has demanded an end to civilian casualties before he agrees to sign a proposed 10-year security agreement with the United States.

AFP Photo/Banaras Khan