China, the United States, Afghanistan and Pakistan have launched their third round of talks 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 on Saturday, 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 would like to see that roadmap to peace emerge by the end of Saturday's meeting.