Zabihullah Mujahid said negotiations had failed due to Islamabad insisting that Afghanistan assume responsibility for Pakistan's internal security, a demand he described as beyond Afghanistan's "capacity".
But, he said, "The ceasefire that has been established has not been violated by us so far, and it will continue to be observed."
On Friday, Pakistani Minister of Defence Khawaja Muhammad Asif said peace talks with Afghanistan in Istanbul aimed at preventing renewed border clashes had collapsed, adding that the ceasefire would hold as long as there were no attacks from Afghan soil.
Afghan and Pakistani troops on Thursday briefly exchanged fire along their shared border, on the same day peace talks resumed in Istanbul.
The militaries from the South Asian neighbours clashed last month, killing dozens, in the worst violence since the Taliban returned to power in Afghanistan in 2021.
Both sides signed a ceasefire in Doha in October, but a second round of negotiations in Istanbul last week ended without a long-term deal due to a disagreement over militant groups hostile to Pakistan that operate inside Afghanistan.
For decades, Pakistan and the Taliban enjoyed warm ties, but relations have deteriorated sharply in recent years.
The October clashes followed Pakistani air strikes earlier in the month on Kabul - among other locations - targeting the head of the Pakistani Taliban.
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