Before heading for Tehran, Annan paid a visit to Syria where he had “constructive” talks with Syrian President Bashar al-Assad in Damascus on Monday.
"I just had a positive and constructive discussion with President Assad," the special envoy said and reiterated the importance of halting violence and promoting political dialogue in Syria.
Syria has been experiencing unrest since mid-March 2011. The violence has claimed the lives of many people, including security forces.
The West and the Syrian opposition accuse the government of killing protesters, but Damascus blames ‘outlaws, saboteurs, and armed terrorist groups’ for the unrest, asserting that it is being orchestrated from abroad.
In March, the former UN secretary general presented the six-point peace plan to end the turmoil in Syria.
On July 7, Annan said more attention should be paid to Iran's role in international efforts to find a solution to the Syrian crisis.
In an interview with the French daily Le Monde, he said more attention needs to be paid to the role of longtime Syrian ally Iran.
