(CNN) -- Iran won't be attending this week's international peace conference on Syria because it won't embrace the framework laid out in a previous conference, U.N. and Iranian officials said Monday. 

The last-minute invitation to Iran, a leading Syrian ally, had threatened to derail the talks after the leading Syrian opposition group and the United States spoke out against it. Louay Safi, a spokesman for the Syrian National Coalition, called Iran's attendance "a deal-breaker." 

Iran announced Monday afternoon that it would not accept "any preconditions" for joining the talks, slated to begin Wednesday in Switzerland. That includes acceptance of the communique issued at the first Geneva conference in 2012, said Mohammad Khazaee, Tehran's U.N. ambassador. 

"If the participation of Iran is conditioned to accept Geneva I communique, Iran will not participate in Geneva II conference," Khazaee said in a written statement Monday afternoon. Foreign Minister Javad Zarif had made a similar declaration on Iranian state TV earlier Monday. 

U.N. Secretary-General Ban Ki-moon, who issued the invitation Sunday, believed he had Iran's assurance that it accepted the original Geneva declaration, his spokesman, Martin Nesirky, told reporters. 

"The secretary-general is deeply disappointed by Iranian public statements today that are not at all consistent with that stated commitment," Nesirky said.The declaration "remains the internationally agreed framework for ending the crisis," he said -- and without Iran's acceptance, this week's conference "will proceed without Iran's participation," he added. 

The goal of the talks is to set up a transitional government to help end the violence that has wracked the country. 
What did Iran announce?
Iran announced Monday afternoon that it would not accept "any preconditions" for joining the talks