Iranian President Hassan Rouhani accused Arab and Western governments of miscalculating in their backing for Syrian rebels as the US-led coalition against the Islamic State group gathered in Paris Tuesday.
Speaking at a reception for Syria's visiting parliament speaker Jihad al-Lahham, Rouhani renewed Tehran's longstanding accusation that it was those governments' support for armed insurgency against its Damascus ally that had led to the rise of the jihadists.
"Unfortunately some countries miscalculated and thought that terrorist groups would be a means for them to achieve their objectives, whereas sooner or later they were always going to be affected by the scourge of terrorism themselves," he said.
"After four years of resistance and perseverance, the plan of the enemies of Syria who thought they could dominate it within a few months has fallen apart," government website www.dolat.ir quoted him as saying.
"The government and nation of Iran will stand by the government and nation of Syria till the end."
The head of Iran's Supreme National Security Council, Admiral Ali Shamkhani, echoed the president's comments in his own talks with Lahham.
"Syria is the front line of defence of Islamic lands against... an unbridled wave of takfiri (Sunni extremist) terrorism and weakening it would bring about... an uncontrollable situation for all neighbouring and regional countries," state media quoted him as saying.
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Tehran has provided arms, military advisers and financial support to its Damascus ally in its battle against the four-year-old rebellion that has increasingly become dominated by jihadists of both IS and Al-Qaeda affiliate Al-Nusra Front.
Meeting Lahham, Foreign Minister Mohammad Javad Zarif said supporters of "terrorist groups" have become isolated and are being forced to cooperate with Syria.
"They have realised they cannot ensure security and have influence in the region only with money and by selling their toys of war," he added, quoted by state news agency IRNA.
Leaders of the US coalition that has been waging an air war against IS in both Syria and neighbouring Iraq met in Paris on Tuesday to review strategy after a string of recent advances by the jihadists.
Iraq's allies pledged support for Prime Minister Haider al-Abadi's plan to recapture the strategic western city of Ramadi from IS.
In a joint statement, the 20 or so coalition representatives also called for the "speedy launch of a UN-facilitated, genuine and inclusive political process" in Syria.