ISLAMABAD -- China, the United States, Afghanistan and Pakistan launched their third round of talks Saturday aimed at finding a way to get the warring Taliban to sit and talk peace with the Afghan government.

At the start of talks in the Pakistani capital of Islamabad, Sartaj Aziz, Pakistan's special adviser on foreign affairs, said there should be no preconditions to negotiations yet the Taliban have already said they would not hold direct talks with the Afghan government until they first held talks with U.S. officials.

Previous rounds of the four-country talks have ended with a promise to meet again but Aziz said this time he wants to see the roadmap to peace emerge by the end of Saturday's meeting.

Kabul too expressed its eagerness for results.

"We are desperately waiting to see the immediate effects and results of our quadrilateral meetings and the progress we have made in the two previous meetings," Javed Faisal, deputy spokesman for Afghanistan's Chief Executive Abdullah Abdullah, told The Associated Press.

A diplomat attending the peace talks said one of the biggest bumps on the road to peace is identifying those Taliban who aren't interested in peace or with whom the Afghan government considers "irreconcilable" -- their crimes too offensive to be part of a peace process. Another challenge is coming up with a set of confidence-building measures that will be good enough to lure Taliban to the table. The diplomat asked that neither his name nor nationality be used because he was not authorized to talk to the media.

Aziz expressed annoyance during the first round of talks held last month when Faisal issued public statements saying Pakistan was to produce a list of Taliban representatives willing to talk peace. The list never materialized and Aziz chastened officials participating in the talks about speaking to the media.

Aziz said whatever roadmap the four-country meeting agrees upon, it will have to clearly lay out each phase of what is certain to be a multi-phase process. He said there also has to be a way to gauge progress

"We believe our collective efforts at this stage ... have to be aimed at the persuading maximum number of Taliban groups to join the peace talks," said Aziz. "This will contribute to imparting a momentum to the process offering the incentive of political mainstreaming to the insurgent groups, and gradually shrink the space for the irreconcilables."

Pakistan, which is accused by Kabul of allowing Taliban leaders safe havens on its territory, is seen as key to getting the Taliban to the table. Pakistan was one of only three countries to recognize the Taliban government before it was ousted by the U.S.-led coalition in 2001. However Aziz earlier told the AP that Pakistan's influence over the Taliban is overstated, recalling several times that the Taliban ignored Pakistan.

Although few details are available it would appear significant that the heads of the Pakistani and Afghan intelligence agencies met in Islamabad on Thursday ahead of the Saturday's four-country meeting.

Pakistan's intelligence agency, the InterServices Intelligence or ISI, has long been accused by Afghanistan as well as Washington of providing backdoor assistance to Afghanistan's Taliban. Washington has openly accused the ISI of supporting the Haqqani network, a U.S.-declared terrorist group, a charge it denies.

The ISI is believed to be one of the most powerful tools available to influence Taliban leaders to join the process.