Hassan Rouhani
Hassan RouhaniReuters

Iranian President Hassan Rouhani said on Thursday that a Syrian peace conference planned for later this month will fail if Tehran, Damascus's main regional ally, does not participate, reports AFP.

The remarks came ahead of a meeting Monday at which Russia and the United States will discuss Tehran's possible involvement in the talks set to start in Montreux, Switzerland on January 22.

On Monday, United Nations Secretary General Ban Ki-moon started sending out invitations to the peace conference, which has been dubbed “Geneva 2”, but Iran was not on the first list.

"Any trans-regional meeting that is not attended by influential players will be unable to solve the Syria crisis," Rouhani told Russian President Vladimir Putin by telephone, the ISNA news agency reported.

"Thus, the Geneva 2 conference has already failed without it even being started," he added, calling the Russian-U.S. initiated forum "a negotiation show."

On Monday, the Islamic Republic brushed aside a suggestion by U.S. Secretary of State John Kerry that it play a "sideline" role at the negotiations, with foreign ministry spokeswoman Marzieh Afkham calling the proposal insulting.

Russia, which like Iran is a supporter of Syria's embattled President Bashar Al-Assad, supports participation by Tehran.

Ban last month launched a fresh appeal for Iran to take part, but UN-Arab League envoy Lakhdar Brahimi said that the United States was blocking this from happening.

According to ISNA, Putin reiterated Moscow's support for having Iran be at the talks and expressed hope "to convince our allies… that Iran, as a key actor, must be present at the talks."

"We believe any preconditions for Iran's participation are useless and unconstructive," it quoted the Russian leader as saying. That was a reference to Tehran's refusal to sign up to a June 2012 accord calling for a transitional government to replace the Assad regime.

Iran says it supports a political solution to the crisis that has pitted Assad against mostly Sunni rebels.

Throughout the civil war in Syria, Iran has provided Assad with military support during his fight against the rebels.

Former Iranian President Mahmoud Ahmadinejad personally sanctioned the dispatch of officers from the Iranian Revolutionary Guards to Syria to fight alongside Assad’s troops.