CHICAGO: US Secretary of State Hillary Clinton met President Asif Ali Zardari here on Sunday, as both sides haggled over a deal to reopen NATO supply lines into Afghanistan, a US official said.

"Secretary Clinton did meet with President Zardari," said Ben Rhodes, a deputy US national security advisor, on the sidelines of the NATO summit here, but did not provide further details.

Neither Rhodes, nor General John Allen, the commander of the International Security Assistance Force (ISAF) force in Afghanistan, would predict when a deal to reopen the border might be reached.

"I can't tell you when that will occur, obviously sooner is better than later, but I can't tell you when that will occur," said Allen.

However, Allen said that talks between the two sides were a positive sign of improving relations between the United States and Pakistan, which were almost ruptured by the November raid.