Iranian President Hassan Rohani is in Tajikistan on an official visit and is due to attend a ceremony at an Iranian-funded hydropower plant.
Rohani was scheduled to meet with Tajik counterpart Emomali Rahmon in Dushanbe on the morning of September 10 for talks.
Both leaders will then go to the Sangtuda-2 hydropower plant to watch the start-up of the second generating unit there.
Iran has invested some $180 million in Sangtuda-2.
Rohani will remain in Tajikistan for September 11 and 12 to attend the Shanghai Cooperation Organization (SCO) summit.
The SCO comprises China, Russia, Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan.
Iran has observer status.
Rohani is expected to meet with the Russian and Chinese leaders on the sidelines of the summit.