"We stress the peaceful settlement of the Syrian issue," Annan said at a press conference in Tehran on Wednesday after meeting with Iranian Foreign Minister Ali Akbar Salehi.
He described his meeting with Salehi on Syria as positive, and underscored the UN efforts to solve the Syrian issue non-militarily.
Annan also expressed pleasure with Iran's support for the six-point peace initiative proposed by the UN and the Arab League on Syria.
As part of a six-point peace initiative, UN plans to deploy 200-250 unarmed observers. The plan also called on Syrian armed forces to withdraw from protest centers on Tuesday, with a complete end to fighting set for 48 hours later. It also called on armed groups to follow the government's lead.
Just hours before the end-of-day deadline for Syria to implement the ceasefire plan, Annan said Syrian forces had withdrawn from a number of areas.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 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Syrian Foreign Minister Walid al-Mualem said Damascus has already withdrawn its troops from several Syrian cities.
"We have already withdrawn forces and army units from several Syrian provinces,'' Mualem stated.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 ceasefire plan for the country must start simultaneously with the deployment of the international observers to the volatile state.
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 the 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.
Also earlier this month, Iraqi Prime Minister Nouri al-Maliki lashed out at Qatar and Saudi Arabia for arming Syrian rebels.
"We reject any arming (of Syrian rebels) and the process to overthrow the (Assad) regime, because this will leave a greater crisis in the region," Maliki said at a news conference.
"The stance of these two states is very strange," he said in apparent reference to Qatar and Saudi Arabia.
"They are calling for sending arms instead of working on putting out the fire, and they will hear our voice, that we are against arming and against foreign interference."
"We are against the interference of some countries in Syria's internal affairs, and those countries that are interfering in Syria's internal affairs will interfere in the internal affairs of any country," the Iraqi leader added.