Syria's government and opposition coalition came face to face for the first time at the UN-led peace talks in Switzerland on Wednesday, while experts widely predicted a negative outcome for the talks.

The two sides and other major world powers restated contrasting views over the future of President Bashar al-Assad and over who is responsible for the increasing terrorism problems in the country that has suffered three years of civil war.

US Secretary of State John Kerry insisted at the start of the conference that Assad will not be part of any new transitional government.

Syrian Foreign Minister Walid Muallem rebuked Kerry, saying "No one in the world has the right to confer or withdraw the legitimacy of a president, a constitution or a law, except for the Syrians themselves."

Muallem also dubbed the country's opposition "traitors" and foreign "agents" in his speech.

"They claim to represent the Syrian people. If you want to speak in the name of the Syrian people, you should not be traitors to the Syrian people, agents in the pay of enemies of the Syrian people," Muallem said in a strongly-worded speech at the conference.

Opposition leader Ahmed Jarba hostilely accused Assad of war crimes and called on him to immediately hand over power to a transitional government.

"Attending the peace talks has already proved to be  progress," Li Weijian, director of the Institute for Foreign Policy Studies at the Shanghai Institutes for International Studies, told the Global Times, noting that the Syrian government and opposition had refused to sit down for talks before the meeting.

Dong Manyuan, a deputy director of the China Institute of International Studies, told the Global Times that it would be "very hard" for the two sides to reach a consensus due to their widely different opinions on Assad's future in the transitional government.

However, Dong said agreements over humanitarian aid and even a cease-fire might be expected in the peace conference.

"Assad will not go," Syria's information minister Omran al-Zohbi insisted on the sidelines of the peace conference in the Swiss town of Montreux.

"If you want to support Al Qaeda, go ahead."

The Syrian government delegation at the conference said Western powers, who are backers of the opposition, had "encouraged and financed terrorism," warning that the wave of violence could spread beyond the country.

However, the opposition accused that the Assad government is to blame for an increasing terrorism in the country.

Li said both the Assad government and increasing terrorism are the main problems for Western powers and they are still mulling which one would more seriously affect their Syria policies.

Agencies contributed to this story