The nations had agreed to recommence talks at the request of host nation Turkey, two of the sources said.
Negotiation teams from both countries were in Istanbul, two of the sources said, to ensure they did not resume border clashes that have killed dozens in October.
One of the sources, a Pakistani security official, said Islamabad would press its central demand at the talks: that Afghanistan take action against militants using its territory as a safe haven and to plan attacks on Pakistani soil.
Islamabad accuses the Taliban of harbouring the Pakistani Taliban, a separate militant group hostile to Pakistan, allowing them to launch attacks from Afghanistan against Pakistani troops.
Kabul denies this, saying it has no control over the group.
The sources declined to be named as they are not authorised to comment publicly on the issue.
The Afghan Taliban and Pakistan's military and foreign office did not immediately respond to requests for comment.
Dozens were killed in October along the border between Afghanistan and Pakistan in the worst such violence since the Taliban took power in Kabul in 2021.
The clashes began after Pakistani air strikes on Kabul, the Afghan capital, among other locations, targeting the head of the Pakistani Taliban.
The Taliban responded with attacks on Pakistani military posts along the length of the 2600km border, which remains closed.
Both nations agreed to a ceasefire brokered in Doha on October 19, but could not find common ground in a second round of talks mediated by Turkey and Qatar in Istanbul, Afghan and Pakistani sources briefed on the issue told Reuters on Tuesday.
Clashes between the Pakistan military and the Pakistani Taliban have continued throughout the ceasefire period, with multiple fatalities reported on both sides on Sunday and Wednesday.
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