Tanker trucks, used to transport fuel to Nato forces in Afghanistan, are seen parked near oil terminals in Pakistan's port city of Karachi on May 15, 2012. – Photo by AFP

PESHAWAR: Pakistan allowed four containers of office supplies for the US embassy in Kabul to cross into Afghanistan for the first time following a six-month blockade, officials said on Friday.

The trucks were permitted to cross as President Asif Ali Zardari prepares to meet Nato leaders at a key summit in Chicago, accepting a last-minute invitation after his foreign minister indicated Pakistan was willing to call time on the blockade.

Islamabad closed its Afghan border crossings to Nato supplies on November 26 when US air strikes killed 24 Pakistani soldiers, leaving hundreds of containers of international supplies stranded at the port in Karachi and plunging relations with Washington to a new low.

The four trucks of US embassy supplies crossed Pakistan's northwest Torkham border into Afghanistan, the officials told AFP on condition of anonymity because they were not allowed to release the information to the media.

“I can't give you the exact number but a lot more will go to Afghanistan in coming days. These all are diplomatic shipments, I mean non-Nato supplies,” one of the officials said.

In Kabul, the US embassy said it could not confirm the shipment.

There were conflicting accounts of when the trucks crossed, with one source saying they began moving earlier in the week and another saying they passed through on Friday.

Almost 300 containers of US embassy supplies, including stationery, computers and printers, are understood to have been stranded in Pakistan by the blockade.

A customs official at the border in Torkham told AFP that they had received a list of 300 containers which would cross into Afghanistan in the coming days.

“I can confirm that three trucks have gone to Afghanistan and there are also reports about the crossing of the fourth one on Friday,” said the official who declined to be named.

“The rest of the containers are also likely to pass in the coming days,” he said.

Pakistan earlier this week said it had ordered officials to finalise an agreement as quickly as possible on lifting the blockade on overland Nato supplies to Afghanistan.

Pakistan and US officials are still negotiating rules, fees and logistics for resuming the Nato transit lines, and Islamabad has not said when Nato supplies will resume.

The United States has guaranteed payment of at least $1.1 billion should the borders reopen as compensation for fighting militants, although Pakistan believes it is owed far more, one source said.

Pakistan is seeking to ease its international isolation and boost its leverage over the future of Afghanistan, as Western countries pull out their combat forces by 2014.

But Islamabad has essentially been forced to climb down on demands for an American apology for the air strikes and an end to drone strikes targeting Taliban and al Qaeda on its soil.

Analysts say Pakistan had no choice but to capitulate to international pressure to reopen the border, with US cash needed to help boost its meagre state coffers as the government prepares to seek re-election.