International envoy Kofi Annan tried to rescue his peace plan for Syria by seeking help Monday from Iran, a staunch ally and military backer of President Bashar Assad's regime.

Before flying to Tehran, Annan said he had agreed on a new approach with Assad to stop the violence, which activists say has killed more than 17,000 people since the conflict began in March 2011.

Annan did not spell out the agreement or say what kind of involvement he saw for Iran in resolving the crisis. Anti-regime fighters dismissed any role for Iran in a plan they and some experts say has little hope of succeeding.

"Kofi thinks you can't have a political transition and solution without the Iranians on board, but this is still part of the understanding that Assad and the regime will be part of the solution — an idea many of us have given up on," said Salman Shaikh, director of the Brookings Doha Center and an analyst on regional politics.

The United States has rejected Iranian participation in international meetings on the crisis in Syria.

Annan, the joint envoy for Syria from the UN and the Arab League, presented a peace plan earlier this year, but it has been deeply troubled from the start.

Government forces and rebels have widely disregarded a cease-fire that was to begin in April, and spreading violence has kept nearly 300 UN observers monitoring the truce stuck in their hotels in Syria.

After a two-hour meeting with Assad on Monday, Annan said the men had agreed on "an approach" to stop the violence, and that the diplomat would share it with the armed opposition.

"I also stressed the importance of moving ahead with a political dialogue which the president accepts," Annan said.

Annan then flew to Tehran to seek help from Iranian officials.

Iran's semiofficial Fars news agency said he would meet with Foreign Minister Ali Akbar Salehi and top security official Saeed Jalili.

Last week, Annan acknowledged that international efforts to find a political solution for Syria had failed and called for a greater role for Iran, saying Tehran "should be part of the solution."

Since Assad took power following the death of his father, Hafez, in 2000, he has deepened cultural, political and economic ties with Iran, making it Syria's strongest regional ally.

Iran has also boosted Assad's military, providing it with advanced communications technology and weapons, as well as sending elite military advisers.

All of this makes Iran unlikely to support change in Syria.

"Inviting Iran to discuss how to best transition to a post-Assad Syria is akin to inviting vegetarians to a barbecue," said Karim Sadjadpour, an Iran analyst with the Carnegie Endowment for International Peace.

Iran will only abandon Assad if it knows the next regime will be as strong an ally and keep Syria an open pathway for Iran to arm Lebanon's Hezbollah militants, Sadjadpour said.

"That's not something that Kofi Annan can offer," he said.

Including Shiite Iran could also further isolate the mostly Sunni rebels fighting inside Syria, who say it is too close to the regime they seek to topple.

"This is not just a war with the regime. It is a war with Iran as well," fighter Ahmed al-Assi said via Skype from Idlib province in northern Syria. "The fall of the regime will be a big blow to Iran. That's why it is given the regime all it needs to fight the revolution."

Syria's uprising began with political protests and has since evolved into an armed insurgency, with scores of rebels groups across the country regularly clashing with government troops and attacking their convoys and checkpoints.

On Monday, the Britain-based Syrian Observatory for Human Rights said its total death toll for the conflict is more than 17,000 people. That includes 11,900 civilians, nearly 900 military defectors and about 4,350 government soldiers.

The group relies on a network of activists on the ground who document deaths and right violations by talking to witnesses and medics and watching amateur videos.

Another group, the Local Co-ordination Committees, says more than 14,800 civilians and rebel fighters have been killed. The group does not report military deaths.

The Syrian government says more than 4,000 soldiers have been killed. It does not provide numbers for civilian dead and bars most media from working in the country.

In a rare interview with the foreign press broadcast Sunday, Assad said most of those killed in Syria were government supporters.

He also told German public broadcaster ARD that the United States is complicit in the killings, saying it backs the opposition he says is made up of armed gangs and terrorists.

A State Department spokesman, Patrick Ventrell, called Assad's comments "ludicrous."

Reports from the ground

Inside Syria, activists reported shelling by government forces and clashes with rebels in opposition areas throughout the country Monday. The Observatory said at least 37 civilians and rebels fighters were killed nationwide, plus at least 24 government soldiers.

At least eight people were killed in government shelling of the city of Ariha in north Syria, it said. In May, rebels succeeded in pushing the army from the city centre, although government forces kept the city surrounded with checkpoints.

Video shot in the city Monday showed a dead man lying on a sidewalk with his head in a pool of blood and four other bodies in a pickup truck.

Another video from northwestern Syria showed at least five dead government soldiers lying in the street, one with an apparent bullet hole in his forehead.

The death tolls and authenticity of the video could not be independently verified.

Russian President Vladimir Putin said Moscow is still committed to the Annan peace plan, adding that the Syrian government and opposition groups should be "forced" to start a dialogue.