Annan was welcomed by Iranian Deputy Foreign Minister for Arab and African Affairs Hossein Amir-Abdollahian upon his arrival at Tehran's Mehrabad airport late on Tuesday night.

The former UN secretary general is scheduled to hold meetings with Iranian President Mahmoud Ahmadinejad and Foreign Minister Ali Akbar Salehi before a press conference on Wednesday.

Iran has announced that it is ready to use all diplomatic means to help resolve the Syria crisis, which has dragged on for over a year.

The Islamic Republic has urged all sides involved in the conflict to engage in dialogue and expressed support for the Syrian government's reform efforts, which have been devised to address the legitimate and peaceful demands of the Syrian people.

Tehran is opposed to any foreign intervention in Syria.

Syria has been experiencing unrest since mid-March 2011, and a large number of civilians and security forces have been killed in recent months.

Western countries and the opposition accuse the government of President Bashar al-Assad of killing people.

Damascus, however, blames "outlaws, saboteurs, and armed terrorist groups" for the unrest, asserting that it is being orchestrated from abroad.

On March 6, Assad said that the Syrian people have "proven their capacity to defend the nation and to build a new Syria through their determination to pursue reforms along with the fight against foreign-backed terrorism."