Ceremonial vice-president Guy Scott is expected in Iran to represent president Michael Sata at the 16th summit of heads of state and government of the Non-Aligned Movement (NAM).
Iran President Mahmoud Ahmadi Nejad will open the summit which has attracted heads of state from all the 120 member states including Zambia.
It is not known why Sata will not attend the summit that will be attended by most dictators of the world.
Foreign Affairs minister Given Lubinda is already in Tehran.
Zambia hosted the Non-Aligned Movement summit in September, 1970.
The movement has 120 member states, 17 observer nations and 10 observer organizations.
The Non-Aligned Movement is a Cold War organization that was supposed to provide a forum for countries that were allied with neither the United States nor the Soviet Union. But since the Soviet Union was dissolved in 1991 the group has struggled for both identity and clout.