"They told us they would not harm us, but they asked us not to work for the Americans."

Rockets were also fired at two vehicles carrying goods intended for delivery to Nato forces as they travelled along the ring road overnight.

The route from Peshawar through the Khyber Pass to the border town of Torkham is the most important supply line for US and Nato forces battling Taliban fighters.

Bryan Whitman, a Pentagon spokesman, said: "The overall impact on our logistical efforts to resupply US forces, Nato forces ... as well as Afghan forces has been small and had an overall insignificant impact to date.

"There's been no direct bearing on our immediate combat capabilities.

Whitman said supplies affected in the latest attack were bound for the Afghan army, not for US or Nato troops.

"While some of our equipment has been interrupted in these cross-border movements, we've still been able to resupply US forces in Afghanistan without any impact on their operations," he said.

Supplies destroyed

On Sunday, a guard was killed in a separate terminal near Peshawar and about 100 lorries and shipping containers were set on fire, police said.

A Pentagon spokesman said the attack had no direct bearing on combat capabilities [AFP]
 
Kifayatullah Khan, the terminal's manager, said 62 of the destroyed containers carried Humvees and other military vehicles for Western forces in Afghanistan.

He said his terminal only handled lorries carrying military supplies for Afghanistan.

The Taliban has carried out a series of such attacks in recent weeks, aimed at disrupting the supply route for US and Nato troops in Afghanistan.

Kamal Hyder, Al Jazeera's correspondent in Islamabad, said security analysts had suggested that the attacks were at least partly due to the fact that Pakistani troops were concentrating more heavily on the eastern border with India.

"One has to remember the Pakistani forces are themselves under attack [in Pakistan's northwestern region] and the military are saying they are not in a position to defend two borders."

Continued attacks

A Taliban spokesman told Al Jazeera two weeks ago that such attacks would continue "until the [Afghan] government and the Americans are smashed".

"We want to show them they are not all-powerful and the mujahidin of Afghanistan can carry out attacks on our enemies in any part of the country," Zabiullah Mujahid, the spokesman, said.

The supply routes are likely to come under further pressure after Jamaat-e-Islami, Pakistan's oldest religious party, announced it would block routes used to supply troops in Afghanistan from December 18.

Talat Hussain, the director of news at Pakistan's AAJ television network, told Al Jazeera that Jamaat-e-Islami's planned protests were an attempt to win a "political advantage".

"Jamaat-e-Islami is trying to cash-in on the sentiment that is already there [in the region] about the supplies that are travelling through there into Afghanistan," he said.

"When collateral damage increases in Afghanistan, and Pakistan's soil also gets hit, there is an increasing frustration among the tribesman [in northwestern Pakistan] and these are the tribesman who are - in alliance with local parties - responsible for these attacks."

International forces have reportedly discussed opening new supply routes into the country through Russia, and even Iran.