WASHINGTON: Pakistan has made some “helpful and positive political statements” in support of an eventual deal to end a blockade of Nato supply lines into Afghanistan, a US official said Wednesday.

But “there are a number of technical issues that we are still working through,” State Department spokeswoman Victoria Nuland said, as talks continued on reopening lines that have been closed for six months.

Pakistan shut its Afghan border crossings to Nato supplies on November 26 after US air strikes killed 24 Pakistani soldiers.

“We have had some progress (in the talks). We've also had some very helpful and positive political statements out of Pakistan, some political moves,”Nuland told reporters.

"While the Pakistani political leadership hasn't yet authorized the reopening of the ground transportation routes, we understand that they did endorse the conclusion of the negotiations," Nuland said.

She added the Pakistanis “are sending a political signal to their own negotiating team that they would like to see this wrapped up. That doesn't change the fact that we still haven't closed all the issues.”Nuland did not elaborate on where stumbling blocks remained.

But she added: “So they see some urgency, we see some urgency, but the negotiators have to finish it.”

When asked if the urgency was to conclude a deal before the Nato summit begins at the weekend in Chicago, she replied: “The urgency is to be able to support Afghanistan from Pakistan.”

Although Islamabad has stopped short of announcing when the transit lines will reopen, it has signaled President Asif Ali Zardari will attend talks on Afghanistan in Chicago on May 20-21, after a last-minute invitation from Nato.