'Rescinding Iran invite a mistake'
Mr Lavrov, speaking at a news conference, reaffirmed Russia's argument that the presence of Iran was essential for the success of the conference which is set to begin in the Swiss resort of Montreux tomorrow.
Iran has been the main regional ally of Syrian President Bashar Assad, supporting his regime with advisers, money and materiel since the uprising began in 2011.
The invitation to Iran extended by Mr Ban on Sunday put the talks in jeopardy, with the US pushing for rescinding the offer and the Syrian opposition threatening to boycott the event entirely.
"This story hasn't helped strengthen the UN authority," Mr Lavrov said at a news conference, adding that recalling the offer looked "unseemly".
The controversy over Iran's participation in the talks reflected deep differences over Syria between the US and Russia, which has been a key ally of Syria, shielding the Assadregime from UN sanctions and continuing to supply it with weapons throughout the civil war that has killed more than 130,000.
Mr Lavrov reaffirmed Russia's stance that the presence of Iran was essential for the success of the talks.
He warned that spurning Iran would deepen division lines in the Islamic world and would have a negative impact on global efforts to fight terrorism.
"The absence of Iran isn't going to help strengthen the unity of the world's Muslims," he said.
He insisted that Russia is not supplying Syria with any weapons which are "banned by international agreements and could destabilise the situation in the region".
At the same time, he voiced hope for the success of the talks that would put the government and the opposition at the same table for the first time since the start of the conflict three years ago.
"There is no catastrophe, we will push for a dialogue between the Syrian parties without any preconditions," he said.
Iran branded the diplomatic about-face "deplorable".
"From our point of view, the withdrawal is deplorable," she said.
Ms Afkham added that Iran expects Mr Ban to explain the "real reasons" for withdrawing the invitation.