Sergey Lavrov said that Ban Ki-moon's decision to withdraw his last-minute offer to Iran to attend the conference set to begin Wednesday in the Swiss resort of Montreux would have a negative impact on the United Nations image.
The invitation to Iran extended by Ban on Sunday put the talks in jeopardy, with the U.S. pushing for rescinding the offer and the Syrian opposition threatening to skip the event entirely.
"This story hasn't helped strengthen the UN authority," 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 United States and Russia, which has been a key ally of Syria, shielding Syrian President Bashar Assad's regime from the United Nations sanctions and continuing to supply it with weapons throughout the civil war that has killed more than 130,000.
He reaffirmed Russia's stance that the presence of Iran was essential for the success of the talks.
Iran has been Assad's main regional ally, supporting his regime with advisers, money and materiel since the uprising began in 2011.
Lavrov 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.
Lavrov insisted that Russia is not supplying Syria with any weapons that are "banned by international agreements and could destabilize the situation in the region."
At the same time, Lavrov 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.
Want to enjoy 'Zen' reading - with no ads and just the article? Subscribe todaySubscribe now