Kofi Annan warned on Tuesday that Syria's deadly conflict could spread across the region as he held talks in Iran and Iraq aimed at shoring up support for his tattered peace plan.
A day after meeting President Bashar al-Assad in Damascus, the UN-Arab League peace envoy had talks in Tehran and Baghdad amid new bloodshed in Syria where more than 17,000 people have reportedly been killed since March 2011.
In Tehran, he stressed that the Islamic republic, Syria's staunchest regional ally, has a key role to play, and also sought help from Iraq, another neighbour of Syria.
"Iran can play a positive role," Annan said after meeting Iranian Foreign Minister Ali Akbar Salehi.
"There is a risk that the situation in Syria gets out of hand and spreads to the region," Annan told a news conference with Salehi, who hailed the envoy's "neutrality" and reiterated Iranian support for his mission.
Annan then flew to Baghdad where, he said, he had "very good discussions" with Prime Minister Nuri al-Maliki and later told reporters he would brief the UN Security Council on Wednesday.
"And I'm sure the council will take appropriate action, including the future of UNSMIS, the monitors on the ground, as their mandate comes up on the 21st of July," Annan said of unarmed UN military observers deployed in Syria.
The 300-strong UN Supervision Mission in Syria was suspended in mid-June because of the intense violence.
The former UN chief's Middle East trip follows a meeting of world powers in Geneva late last month - to which Iran was not invited - to salvage his peace initiative.
A plan was agreed in Geneva for a political transition in Syria, which did not make an explicit call for Assad to quit, although the West and the opposition made clear they saw no role for him in a unity government.
After meeting Assad on Monday, the former UN chief said he had agreed with him on a new political "approach" to ending the crisis in Syria that he would put to the rebels.
"We discussed the need to end the violence and ways and means of doing so. We agreed an approach which I will share with the armed opposition," he said.
Deadly violence showed no sign no abating on Tuesday.
The army rained shells down on the rebel-held central town of Rastan as violence killed at least 21 people nation-wide, the Syrian Observatory for Human Rights said. "We have many wounded, and there are no doctors here, only two dentists. We can't do anything for the wounded. It's tragic," an activist in Rastan told AFP via Skype.
Of those killed on Tuesday, at least nine were civilians, four soldiers and four rebels, the Observatory said, noting that 98 people were killed on Monday, including 34 soldiers.
Among the dead was Syrian Arab Red Crescent staffer Khaled Khaffaji, shot by unknown gunmen overnight in the eastern province of Deir Ezzor.
Dr Abdul Rahman al-Attar, president of the organisation, said people were "devastated" by the death. "All sides must respect health-care workers and the Red Cross and Red Crescent emblems, and allow Syrian Arab Red Crescent volunteers to provide assistance unhindered and in safety," a statement said.
Lebanon, meanwhile, began reinforcing its border with Syria following a series of deadly attacks, a military spokesman said in Beirut. Syrian troops traded gunfire with men overnight in the border area and shells fell inside Lebanon, wounding civilians, the army said, just two days after border clashes killed two girls.
Syrian state news agency SANA confirmed the violence and said troops foiled attempts by "armed terrorist groups" to infiltrate from Lebanon during the night.