BEIRUT — 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. Antiregime fighters dismissed any role for Iran in the plan, which they and some analysts 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 a specialist 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 United Nations and the Arab League, presented a peace plan earlier this year, but it has been deeply troubled from the start.
Government forces and rebels widely disregarded a cease-fire that was to begin in April, and spreading violence has kept nearly 300 UN observers, who are supposed to be monitoring the truce, instead stuck in their hotels in Syria.
After a two-hour meeting with Assad on Monday, Annan said that 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, where Iran’s semiofficial Fars news agency said he would meet with Iran’s foreign minister, Ali Akbar Salehi, and its top security official, Saeed Jalili.
Last week, Annan acknowledged that international efforts to find a political solution for Syria had failed, and he called for a greater role for Iran, saying Tehran ‘‘should be part of the solution.’’
Since Assad took power after the death of his father, Hafez, in 2000, he has deepened the 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 abandon Assad only 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 Shi’ite Iran could also further isolate the mostly Sunni rebels fighting inside Syria, who say Tehran 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,’’ said one fighter, Ahmed al-Assi, 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 giving the regime all it needs to fight the revolution,’’ he said.
In a separate development Monday, Russia, the Assad regime’s biggest arms supplier, said it would not sign any new weapons contracts with Syria until the conflict calms down.
But Vyacheslav Dzirkaln, deputy chief of the Russian military and technical cooperation agency, told Russian news agencies that Russia will fulfill all previous contracts.