KABUL: Peace talks between warring Afghan factions are expected to start as soon as they iron out their main differences over the release of the "most dangerous" Taliban prisoners, officials and sources from both sides said.

Despite a major push by the United States, there has been a delay in the intra-Afghan talks as the Afghan government and some key NATO members are uncomfortable about the release of Taliban commanders accused of conducting large-scale attacks that killed civilians in recent years.

An Afghan government source said the prisoner issue had largely been resolved and they would release an alternative set of prisoners with talks expected to start mid-July.

"The Taliban agreed because it was delaying the talks," he said, adding the government had also demanded a guarantee from the Taliban that it was no longer holding any Afghan security force prisoners.

A source close to the Taliban said the group was willing to move forward so long as most of the 5,000 prisoners demanded were released. "I don't think releasing or not releasing 200 or 300 prisoners will matter in the process, the Taliban can agree for (those) prisoners to remain in Afghan government custody," the source said.