Which country declared joint border 'reaction force' with Pakistan?

Iran's President Hassan Rouhani announced that Iran and Pakistan to create a joint 'reaction force' on the border between the two countries, for combatting terrorism. The announcement came during a two-day visit to Iran by Pakistani Prime Minister Imran Khan, the first of his tenure. Iran and Pakistan share a 959 km land border. Balochistan, which borders Afghanistan and Iran, is Pakistan's largest and poorest province, rife with ethnic, sectarian and separatist insurgencies.