The controversy began Sunday when U.N. Secretary-General Ban Ki-moon announced -- much to the displeasure of the United States and Syrian rebel groups -- regional power Iran, a close ally of Syrian President Bashar Assad, would have a seat at the table Wednesday at the outset of what's being called the Geneva II conference in Montreaux, Switzerland.
Bowing to intense American pressure, Ban's spokesman said Iran would not be there.
"Given that it has chosen to remain outside that basic understanding, he has decided that the one-day Montreux gathering will proceed without Iran's participation," Ban's spokesman said in the statement.
The reversal came after the Syrian National Coalition threatened to back out of the Geneva II talks.
"This is a deal breaker for the National Coalition. If they insist to bring Iran, we will have to go back to the drawing board again," Syrian National Coalition spokesman Louay Safi told CNN. "We don't want to negotiate with Iran. We want to negotiate with the regime. Before we go [to the conference], Iran has to say they will pull out all the fighters [inside Syria] allied with it," Safi said.
Iran, which has supported Assad with weapons and paramilitary fighters in the years-long civil war, said it would come after Ban's invitation.
The last-minute addition was seen as highly controversial after the exiled Syrian National Coalition, a group recognized by western nations as a potential leadership authority in a post-Assad Syria, threatened to back out after months of behind-the-scenes arm-twisting to get them into peace negotiations in the first place.
Now, the New York Times said, Iran is out. And the BBC said the SNC is back in.
Ban's decision to include Iran was suspect because the country seemingly does not support the stated goal of Geneva II: to create a caretaker government acceptable to both Assad and Syrian rebel forces to take control of the country before elections can be held.
That road map was first laid out during an international conference on the Syria conflict, known as Geneva I, held in Geneva, Switzerland, on the other side of the lake, in June 2012.
Iran's position on the caretaker government isn't particularly clear at this point, the Times said. Ban, in announcing Iran's invitation, said he was assured privately the Iranians found the premise of the peace talks acceptable. Statements on Iranian state-run television suggested otherwise.
"We have always rejected any precondition for attending the Geneva II meeting on Syria," a spokeswoman for the Iranian Foreign Ministry said. "Based on the official invitation that we have received, Iran will attend the Geneva II [conference] without any preconditions."
For his part, Assad has threaded a fine line in pledging to participate in the talks. He has publicly said he will not step down from power and has suggested if there are new elections he will stand for them, though western forces have made his leaving power a precondition.
Assad's government then walked back a Russian media report that quoted Assad as telling a Russian delegation his leaving power was "not up for discussion."
The report by the non-governmental Interfax news agency was "inaccurate," Syria's official Syrian Arab News Agency said, quoting Assad's media office without elaborating.
Syrian state television broadcast the same report.
Russia is another key Assad ally.
The two Syrian news outlets quoted the media office as saying Assad did not give an interview to Interfax.
Interfax quoted him as telling a visiting delegation of Russian Parliament members and religious and social figures he and his regime were here to stay and saying the issue of his regime's removal would be a non-starter at the first talks between the regime and the opposition aimed at ending the country's nearly 3-year-old civil war.
The talks are to begin Wednesday in Montreux, Switzerland, on Lake Geneva at the foot of the Alps.
"If we wanted to give up, we would have done so at the very beginning," Interfax quoted Assad as saying. "We are on guard for our country. This issue is not up for discussion."
The Western-backed Syrian National Coalition voted by a narrow margin Saturday to take part in the talks after facing heavy U.S. and British pressure.
"We will go to Geneva II without compromising any principles of our revolution," coalition President Ahmed Jarba said.
The talks will be the Assad regime's "funeral," he said.
Syria told Ban last week its intention for the talks was fighting "terrorism." The regime uses that term to describe the armed opposition.
U.S. Secretary of State John Kerry hailed the opposition coalition's decision to participate in the talks as "a courageous vote in the interests of all the Syrian people who have suffered so horribly under the brutality of the Assad regime and a civil war without end."
More than 100,000 people have been killed in the war, more than 2 million Syrians have fled their homes and more than 9 million are in need of humanitarian aid, the United Nations says.