Talks are taking place between the Taliban and the main tribe controlling a strategically important part of northern Pakistan, tribal sources say.
Correspondents say the negotiations could result in the Taliban having access to the remote north-western Pakistani tribal district of Kurram.
Its western tip is only 90km (56 miles) from the Afghan capital, Kabul.
If a deal is reached it could have major implications for Nato's operations in Afghanistan.
Pakistani officials confirmed to the BBC's M Ilyas Khan in Islamabad that members of the Haqqani network - a branch of the Afghan Taliban based in Pakistan - were holding the talks with representatives of the Turi tribe.
The Turis are the main tribe of Kurram tribal region.
Our correspondent said that the specific terms of any proposed deal were not known but the broad outline was simple - the Taliban guarantees the safety of Turis travelling overland from their Kurram heartland to Peshawar.
In return the militants would be allowed access to Kurram to launch operations around Kabul.
The Turi tribe, which belongs to the Shia sect of Islam, has traditionally abhorred the Taliban - who adhere to a hardline Sunni form of the faith. Many consider Shias to be non-Muslims.
Two years ago, the Turis fought a major battle with the Taliban in Kurram and are now consolidating their hold on most of the region.
A Taliban-imposed blockade of Kurram in the aftermath of the fighting - which effectively has cut the area off from the rest of Pakistan - has caused immense suffering to Turi people.
Trade worth millions of dollars has been lost and Turi people are able to leave Kurram only in convoys which are regularly attacked.
The Taliban have approached the Turis in the hope of making a deal four times since 2008 - each time upgrading the status of their negotiating team.
But a deal so far has proved elusive.
That is principally because Turi elders - while welcoming the prospect of the blockade being lifted - expressed inability to guarantee the safety of the Taliban if they travelled through Kurram.
Our correspondent say that there are no signs they have eased their views during the latest two rounds of talks in Peshawar and Islamabad.
Even if a deal is made, our correspondent says, elders will find it hard to sell it to Turi tribesmen who want revenge against the Taliban, not concessions.