Two teams, nominated by the government and the Tehreek-e-Taliban Pakistan (TTP), were due to gather in Islamabad at 2:00pm (0900 GMT) to chart a preliminary "roadmap" for the talks on Tuesday. This was meant to pave the way for the beginnings of the peace talks.
However, Al Jazeera's Kamal Hyder, reporting from Islamabad, said the meeting was unlikely to go ahead as scheduled.
"This morning it was a done deal but now we are told the government committee wants clarification from the Taliban committee on certain issues so the formal meeting is not going to happen today," he said.
Last week, Prime Minister Nawaz Sharif named a team to begin dialogue with the Taliban, who have been waging a violent insurgency since 2007.
Many observers had been anticipating a military offensive against TTP strongholds in Pakistan's tribal areas, following a bloody start to the year on both sides, with the government responding to Taliban violence with raids on Waziristan strongholds.
More than 110 people were killed in attacks in January, many of them military personnel.
Critics have accused Sharif's government of dithering in response to the violence.
The TTP has said in the past that it opposes democracy and wants Islamic sharia imposed throughout Pakistan, while the government has stressed the country's constitution must remain paramount.
The TTP had asked cricketer-turned-politician Imran Khan to be part of their team but he declined.
The two sides held separate meetings in Islamabad on Monday and later decided to talk each other on Tuesday, Khan said.