During his stay in Iran, Annan will hold talks with Iranian officials including Iranian Foreign Minister Ali-Akbar Salehi about Syria.
Speaking at a press conference at the airport in Hatay province in Southern Turkey earlier Tuesday, Annan said there should be no preconditions to halting violence in Syria and insisted a UN-sponsored peace plan designed to stem 13-months of conflict was still on the table.
Just hours before the end-of-day deadline for Syria to implement the ceasefire plan, Annan said Syrian forces had withdrawn from a number of areas.
Earlier on Tuesday Syria's foreign minister, speaking at a joint press conference with his Russian counterpart Sergei Lavrov in Moscow, said Damascus wanted guarantees from Annan that armed groups attacking its troops would commit to a ceasefire.
Syrian Foreign Minister Walid al-Mualem said Damascus has already withdrawn its troops from several Syrian cities.
"We have already withdrawn forces and army units from several Syrian provinces,'' Mualem stated.
The top Syrian diplomat reiterated that the United Nations cease-fire plan for the country must start simultaneously with the deployment of the international observers to the volatile state.
As part of a six-point peace initiative, UN plans to deploy 200-250 unarmed observers. The plan also calls on Syrian armed forces to withdraw from protest centers on Tuesday, with a complete end to fighting set for 48 hours later. It also calls on armed groups to follow the government's lead.
The Russian foreign minister, for his part, urged the armed opposition groups and their supporters to bring about the cease-fire.
The Russian top diplomat also expressed Moscow's readiness to send its own observers to Syria to assist the UN mission.
"The key issue for the success of the special emissary of the United Nations Kofi Annan in Syria is the dispatch of international observers," Sergei Lavrov went on to say.
Last week, Syria took Qatar, Saudi Arabia, Turkey and the West responsible for undermining the peace plan proposed by the UN-Arab League envoy and urged stronger international support for the plan.
Speaking after Annan briefed the UN General Assembly, Syria's Ambassador to the United Nations Bashar al-Jafari criticized Persian Gulf Arab states for their "petrodollar" support for Syrian opposition groups and lashed out at Turkey for hosting the second so-called "Friends of Syria" meeting last weekend.
"We need to get commitments from the Qataris, from the Saudis, from the Turks, from the French, from the USA, that Annan should be given a chance in order to succeed," Jafari said.
"We need a crystal-cut commitment and a guarantee by Mr. Annan himself - after he consults with Qatar, Saudi Arabia, Turkey and the others - that once the government will observe and will respect the end of violence, the other parties will do the same and will not fill the vacuum," he added.
Annan told the UN General Assembly on Thursday that the Syrian government told him it had started a "partial withdrawal" from cities of Idlib, Zabadani and Daraa.
The International Committee of the Red Cross said Damascus has agreed to give the organization access to prison facilities across Syria.