Amid rising focus on Iranian Kurdish opposition groups based in Iraqi Kurdistan, Tehran says Baghdad has agreed to its demand that such factions be disarmed and relocated. But as the Islamic Republic’s Sept. 19 deadline for action against its exiled Kurdish opponents looms, there are major questions about the extent to which any agreement may be implemented. This comes as the authorities in Iraqi Kurdistan worry that the deal is aimed at further undermining their self-rule and standing in the regional geopolitical landscape.

In March, then-secretary of Iran’s Supreme National Security Council Ali Shamkhani and his Iraqi counterpart Qasim Al-Araji signed an agreement in Baghdad to secure the border between the two countries. The accord was primarily aimed at curbing the activities of Iranian Kurdish opposition parties in the Kurdistan region of Iraq.

Addressing reporters in Tehran on Aug. 28, Iranian Foreign Ministry spokesman Nasser Kanani said the Iraqi central government had committed to disarm “terrorist, secessionist groups” and close their “bases” by...