Taliban representatives and the government of Afghan President Hamid Karzai have begun secret, high-level talks over a negotiated end to the war, according to Afghan and Arab sources.

The talks follow inconclusive meetings, hosted by Saudi Arabia, that ended more than a year ago. While emphasizing the preliminary nature of the current discussions, the sources said that for the first time they believe that Taliban representatives are fully authorized to speak for the Quetta Shura, the Afghan Taliban organization based in Pakistan, and its leader, Mohammad Omar.

"They are very, very serious about finding a way out," one source close to the talks said of the Taliban.

Although Omar's representatives have long publicly insisted that negotiations were impossible until all foreign troops withdraw, a position seemingly buoyed by the Taliban's resilience on the battlefield, sources said the Quetta Shura has begun to talk about a comprehensive agreement that would include participation of some Taliban figures in the government and the withdrawal of U.S. and NATO troops on an agreed timeline.

The leadership knows "that they are going to be sidelined," the source said. "They know that more radical elements are being promoted within their rank and file outside their control. . . . All these things are making them absolutely sure that, regardless of [their success in] the war, they are not in a winning position."

Karzai's spokesman, Waheed Omer, said Wednesday that "negotiations, in a substantial way, have never happened."

"There have been contacts, initiated sometimes by the Taliban themselves, at different levels," he said. But, he added, the exchange "remains at the level of contacts, because negotiations is a term that involves people talking about their conditions, different things related to a settlement."

On Thursday, Karzai will inaugurate the first meeting of the government's new "high peace council," a group of about 70 Afghans that is intended to form policy on how to pursue negotiations with the Taliban. Omer said there will be "no backdoor negotiations" outside the work of this group because "we do not want to undermine the high peace council."

A half-dozen sources directly involved in or on the margins of the secret talks agreed to discuss them on the condition of anonymity. All emphasized their preliminary nature, even as they differed on how specific they have been. All expressed concern that any public description of the meetings would undercut them.

"If you talk about it while you're doing it, it's not going to work," said one European official whose country has troops in Afghanistan.

Several sources said the discussions with the Quetta Shura do not include representatives of the Haqqani group, a separately led faction that U.S. intelligence considers particularly brutal and that has been the target of recently escalated U.S. drone attacks in northwestern Pakistan.

The Haqqani group is seen as more closely tied to the Pakistani intelligence service than the Quetta Shura, based in the southwestern Pakistani province of Baluchistan. But one Afghan source, reflecting tension between the two governments, said Pakistan's insistence on a central role in any negotiations has made talks difficult even with the Quetta group. "They try to keep very tight control," this source said of the Pakistanis.