Syria's government and opposition angrily spelled out their hostility Wednesday when they met for the first time at a U.N. peace conference, as world powers also offered sharply divergent views over President Bashar al-Assad's future.
The United States and the Syrian opposition opened the talks in the Swiss city of Montreux by saying Mr. Assad had lost his legitimacy when he crushed a once-peaceful protest movement.
Opposition leader Ahmad Jarba accused the Syrian leader of Nazi-style war crimes and said the Western-backed Syrian National Coalition would never accept a role for him in a transitional administration.
In a strong response, Syrian Foreign Minister Walid al-Moallem said terrorists and foreign meddling had ripped his country apart.
The U.S. State Department called Moallem's speech "inflammatory," saying it was not in line with the aims of the gathering, intended to begin the process of forming a transitional government.
Moallem refused to give up the podium, despite requests from Ban Ki-moon, who asked him to refrain from inflammatory statements. Moallem angrily told the U.N. chief, "You live in New York. I live in Syria, I have the right to give the Syrian version here in this forum. After three years of suffering, this is my right.''
U.S. Secretary of State John Kerry echoed the rebel view that it is impossible for Mr. Assad to stay under the terms of a 2012 international accord calling for an interim coalition.
"There is no way, no way possible in the imagination that the man who has led the brutal response to his own people could regain the legitimacy to govern."
Russian Foreign Minister Sergei Lavrov challenged the U.S. insistence that Mr. Assad be excluded from a possible transitional administration, saying all sides must have a role and criticizing "one-sided interpretations" of the 2012 pact.
Saudi Arabia, which backs the Sunni rebels, called for Iran and its Shi'ite Lebanese ally Hezbollah to withdraw forces from Syria.
But Iranian representatives were notably not among the more than 40 delegations invited to the conference, shunned by the opposition and the West for rejecting calls for a transitional government. Its president said Tehran's exclusion meant the talks were unlikely to succeed.
U.N. Secretary-General Ban Ki-moon opened the conference saying the challenge of finding a peaceful solution to the crisis is "formidable," but that having the Syrian parties present raises hope.
"After nearly three painful years of conflict and suffering in Syria, today is a day of fragile, but real hope. For the first time, the Syrian government and the Syrian opposition, countries of the region and the wider international community are convening to seek a political solution to the death, destruction and displacement that is a dire reality in Syria today."
The first two days of talks will give the delegations an opportunity to address the peace effort before the process shifts Friday to discussions in Geneva between only the Syrian sides and U.N.-Arab League envoy Lakhdar Brahimi.
Meanwhile, during the speeches fighting in Syria continued unabated. The Syrian Observatory for Human Rights reported clashes and air strikes around the country.
Nearly nine million people - almost 40 percent of Syria's population - have been displaced by the fighting. According to U.N. relief officials an estimated 250,000 people in Syria are out of the reach of aid deliveries. Millions more live in areas that are barely accessible.