CHICAGO: US-Pakistani talks on reopening vital supply routes for Nato forces in Afghanistan have faltered over Islamabad's “unacceptable” demand to charge steep fees for trucks crossing the border, a senior US official told AFP Sunday.

Pakistan also has failed to present a coherent, consistent position in the negotiations, said the official, who spoke on condition of anonymity.

The US official said “to some extent it's something the Pakistanis will have to work out themselves.”

”Inside the Pakistani government, they need a consolidated proposal for what to put on the table.”

The official confirmed that Pakistan has proposed an exponential increase in fees, from the current rate of about $250 per truck to “thousands of dollars.” "That's, in a word, unacceptable," he said.

The proposed fees were a concern not only for the United States but other Nato countries with troops in Afghanistan, the official said, as the alliance plans a gradual withdrawal of most combat forces over the next two years.

Asked if the United States was willing to consider a dramatic hike in border fees, the official said: “Not when seven or eight months ago we were paying a small fraction of that figure.”

The United States still expected to work out a deal eventually on the border crossing but hopes had faded for an agreement that could be announced before or during Nato's summit in Chicago on Sunday and Monday, the official said.

“I think you'll see a resolution soon but it will take a little more work,”he said.

After botched US air strikes killed 24 Pakistani soldiers in November, Pakistan shut the Torkham border gate on its northwest border, forcing Nato to rely on northern routes and cargo aircraft to ferry supplies and troops into Afghanistan.

Talks scheduled in Chicago between Nato Secretary General Anders Fogh Rasmussen and Pakistani President Asif Ali Zardari were canceled Saturday.

Both Nato and Pakistani officials insisted to AFP that the last-minute delay in the planned meeting was due to the late arrival of Zardari's flight from London.