The United Nations has invited Iran to attend crucial Syria peace talks after it pledged to play a "positive and constructive role" but the surprise move provoked a pull-out threat from the Syrian opposition and caution from the US.
In a hastily called press conference at the United Nations headquarters on Sunday evening, Ban said he "strongly" believes that Iran "needs to be part of the solution to the Syrian crisis" as he has been striving to generate momentum and create the "best possible atmosphere" for the success of the "crucially important" effort to end the Syrian war.
Ban said he has "spoken at length" in recent days with Iran's Foreign Minister Javad Zarif, who he said agreed that the goal of the negotiations is to establish, by mutual consent, a transitional governing body with full executive powers.
"It was on that basis that Foreign Minister Zarif pledged that Iran would play a positive and constructive role" in the Geneva II Conference which is to begin on Wednesday in Montreux, Switzerland.
Ban said Zarif assured him that Iran "understands that the basis of the talks is the full implementation of the June 30, 2012 Geneva Communique, including the Action Plan.
"Therefore, as convenor and host of the conference, I have decided to issue an invitation to Iran to participate," Ban told reporters.
Following the announcement, Syria's opposition said in a Twitter message that it would not attend unless Ban withdrew invitation to Iran.
"The Syrian coalition announces that they will withdraw their attendance in Geneva 2 unless Ban Ki-moon retracts Iran's invitation," Louayb Safi, a coalition spokesman, said in a Twitter message.
The US too expressed concern and said it views Ban's invitation to Iran as "conditioned on Iran's explicit and public support for the full implementation of the Geneva communique including the establishment of a transitional governing body by mutual consent with full executive authorities".
Iran had earlier refused to accept a communique adopted by the major powers in Geneva on June 30, 2012 calling for a transition government in Syria.
American officials said they had been in regular communication with the UN over the requirements Iran would need to meet to be invited, but they appeared to have been caught off guard by Ban's announcement.