The delay is seen as a setback to campaigns to win backing from religious leaders for the Afghan peace process, The Express Tribune reported Thursday.
The Ulema Conference had been scheduled for the end of January in Kabul. Ambassador Omer Daudzai said Wednesday neither Afghanistan nor Pakistan was prepared for the conclave.
He said the conference would be rescheduled for some time in February.
Daudzai said a delegation from the Afghan organizing committee would visit Islamabad soon to discuss an agenda with a five-member Pakistani organizing committee.
Afghan High Peace Council Chairman Salahuddin Rabbani proposed the conference when he visited Pakistan's capital in November.
The Afghan Taliban have called the conference a part of "American intrigues" and urged religious leaders from several Middle Eastern counties not attend.