The Taliban has a responsibility to honour Afghans' yearning for peace, according to a letter purportedly by Taliban shadow chief justice Mawlawi Abdul Hakim.
The fence will curtail cross-border militant movements and pave the way for better relations, officials say.
The latest group of 135 former militants, many of them teenagers, completed de-radicalisation training in South Waziristan last month and plan to open businesses or join the army.
The attacker, allegedly linked to Tehreek-e-Labaik Yah Rasool Allah Pakistan, was arrested after wounding Interior Minister Ahsan Iqbal.
The Kremlin is backing Tehran's sectarian agenda in an attempt to claw its way back into relevancy in the Middle East, Afghanistan, Central Asia and beyond.
Pakistani security forces raided the foundation's compound twice and arrested at least four members on suspicion of links to Iran's Islamic Revolutionary Guard Corps (IRGC) and Tehran's ongoing recruitment of Pakistani Shia to fight in Syria.
Iranian plotters have for the second time in three months attempted to use the Taliban to attack the Turkmenistan-Afghanistan-Pakistan-India natural gas pipeline -- a project Tehran adamantly opposes.
The Pakistani army transferred security duties to the civilian government of Upper and Lower Dir districts April 11.
The flag meeting at the Torkham border crossing comes after a brief flare-up of violence earlier along the border. Such meetings will improve communication and defuse tensions, say observers.
Tribal elders and local officials quickly de-escalated the situation, saying fighting along the border benefits only terrorists.