The United States responded with surprise on Sunday night to United Nations secretary-general Ban Ki-moon's decision to invite Iran to a major peace conference on Syria, just two days before the summit is scheduled to begin in Geneva.Iran promptly accepted a role in the Geneva II conference on Sunday night after Ban invited Iranian Foreign Minister Mohammad Javad Zarif to participate in the talks based on "extensive" private communications between the two men.The conference is scheduled for January 22, and will include participation from the government of embattled Syrian President Bashar Assad as well as the organized opposition fighting for his ouster. A spokesman for Ban told reporters last week that an invitation would only be extended to Iran if Russian foreign minister Sergey Lavrov and US Secretary of State John Kerry deemed it appropriate, a suggestion that Kerry seemed to warm to earlier this month, saying Iran might be able to help "on the sidelines."However on Sunday, Ban told reporters he had extended a full invitation to Iran, as well as to Australia, Bahrain, Belgium, Greece, the Vatican, Luxembourg, Mexico, the Netherlands, the South Korea."As I have said repeatedly, I believe strongly that Iran needs to be part of the solution to the Syrian crisis," Ban told reporters on Sunday."I have spoken at length in recent days with Iran’s Foreign Minister, Mr. Javad Zarif. He has assured me that, like all the other countries invited to the opening day discussions in Montreux, Iran understands that the basis of the talks is the full implementation of the 30 June 2012 Geneva Communique, including the Action Plan."Ban continued, saying he and Zarif had agreed the goal of the talks should be to establish a "transitional governing body with full executive powers...by mutual consent." The US responded in a statement by State Department spokeswoman Jen Psaki saying, "if Iran does not fully and publicly accept the Geneva communiqué, the invitation must be rescinded.""The United States views the UN Secretary General’s invitation to Iran to attend the upcoming Geneva conference as conditioned on Iran’s explicit and public support for the full implementation of the Geneva communiqué including the establishment of a transitional governing body by mutual consent with full executive authorities. This is something Iran has never done publicly and something we have long made clear is required."The Iranian delegation has not yet commented, beyond accepting the invitation.