The meeting in Chicago opened Sunday amid a standoff over Pakistan's closure of key roads used to truck supplies to NATO bases in Afghanistan in protest of the friendly-fire airstrike by U.S. warplanes that killed two dozen Pakistani troops along the border in November.
There was hope an agreement would be struck at the Chicago summit, which will be attended by both President Obama and Pakistani president Asif Ali Zardari. But a White House spokesman said late Saturday the two leaders had no plans to meet on the sidelines of the summit.
"We're not anticipating necessarily closing out those negotiations this weekend," White House Deputy Press Secretary Ben Rhodes told reporters, adding that most of the detail work was being handled below the presidential level.
"It's our sense that both sides want to get it done, it will get done," Rhodes said. "But right now, we're in a process of negotiation about how exactly that's going to happen."
Some U.S. official said the primary sticking point was over money. Pakistan is holding out over the price NATO should pay Pakistan per truck and is also seeking higher payments for road maintenance and an indemnity for damage to cargo, The New York Times said Sunday.
Diplomatic officials told The Times the failure to return to Pakistan with a favorable deal was a potential embarrassment to Zardari and could aggravate the often strained relations between Pakistan and the United States.