CHICAGO - The US commander in Afghanistan told Reuters he would not be disappointed if a long-sought agreement with Pakistan on supply routes failed to materialise by the end of the Nato summit in Chicago on Monday.

General John Allen, who is also the top Nato commander in Afghanistan, said in an interview he was confident a deal would eventually be struck but “whether it’s in days or weeks, I don’t know.”

Many Obama administration officials had hoped for an agreement with Islamabad in time for the Sunday-Monday summit that would end a nearly six-month ban prohibiting trucks in Pakistan from carrying supplies to Nato forces in neighbouring Afghanistan.

Asked if he would be disappointed if Pakistan - whose president will attend the summit - didn’t strike an agreement before the end of the Chicago talks, Allen said: “No.”

“I don’t need the (ground supply lines) to be open to support the campaign. But they’re helpful to us in sending home our equipment,” Allen said.

“We don’t want an agreement fast, we want an agreement that’s right. So we’re going to take the time to get it right.”

Allen faces an extremely difficult task, preparing for the withdrawal of most Nato troops by the end of 2014 even as he continues to build up Afghan security forces and move territory under their control. His strategy has been to speed that transition, while enough US forces are still there to help the Afghans when needed.

“Getting as much of that early in the process as we can, so I’ve got enough combat power here to support (the Afghans) during that early part of the transition’s really important,” he said.

Allen will complete the removal of all US surge troops this fall, leaving a US force of about 68,000. He is then due to make recommendations for additional troop reductions after the summer combat season, which should reveal how well Afghan forces can fight - and how well Nato fares with a force smaller than the one that claimed swathes of southern Afghanistan in a troop-heavy, counterinsurgency campaign in 2010.

But the presidential victory in France of Socialist Francois Hollande, who has promised to pull French combat troops from Afghanistan this year, raises questions. Hollande repeated that pledge during his inaugural visit to Washington last week and said an extremely limited number of troops would remain to train Afghan forces and bring back equipment beyond 2012.

Allen said Hollande’s plans to accelerate the withdrawal would not affect his strategy. “It’s a sovereign decision of France. And we’ll work with them and to support whatever decision ultimately they make,” he said.

Allen said he believes the summit in Chicago will demonstrate a long-term commitment to Afghanistan’s military, allowing Nato to avoid making the same mistake that the Soviet Union did after its withdrawal more than two decades ago.

“After the Soviet Union departed Afghanistan, that army survived for a short period of time. But it was unsupported. And unsupported, it eventually collapsed,” Allen said, pointing to the ensuing civil war and rise of the Taliban.

“The trajectory we are on right now, I am confident, will prevent history from repeating itself.”