The three-day meeting ending Friday was marked by fierce debate on the government's plan to end the country's long civil war and a bombing attempt in the streets of Kabul, the BBC reported.
Observers say there is little indication the Taliban are inclined to deal, the British broadcaster said.
The militant group's key demand is that all foreign forces withdraw from Afghanistan before any negotiations can begin. The Taliban have been battling to overthrow the U.S.-backed government and drive out the 130,000 foreign troops stationed in Afghanistan.
Afghan President Hamid Karzai wanted to use the conference of about 1,600 delegates to enlist support for his plan to offer economic incentives to reformed Taliban militants. He has proposed offering amnesty and reintegration incentives to people who leave the organization.
Karzai also offered to negotiate the removal of some Taliban from a U.N. blacklist and to give certain leaders asylum in another Islamic country so peace talks could be conducted.
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