Syrians from a wide spectrum of opposition to President Bashar al-Assad began meeting in Doha Thursday to hammer out a government-in-waiting world powers will accept as credible and representative.

Ahmed Ben Helli, deputy head of the Arab League which with Qatar is brokering the meeting, told reporters that delegates had been urged to overcome the sharp divides that have dogged their efforts to unseat Assad.

"The opposition is urged to agree on a leading body which would have credibility among the Syrian people and the international community," Ben Helli said.

His comments were echoed by Qatar's Prime Minister Sheikh Hamad bin Jassem Al-Thani who, on opening the meeting, called on Assad's opponents to "unify their ranks and positions and to prioritise the interests of their nation and people over their own personal interests."

Burhan Ghalioun, former leader of the main exiled opposition group, the Syria National Council (SNC), told reporters the meeting could last two or three days.

"The atmosphere is positive. Everyone wants (the meeting) to succeed, failure is forbidden," he said.

Washington wants the opposition to reshape into a widely representative government-in-exile, while opposition leaders say such a body could be sited outside the country or in zones of Syria now under the control of armed rebels.

Representatives from a number of countries, including the United States, Britain, France, and Germany, are attending the meeting alongside Arab League chief Nabil al-Arabi and Gulf Cooperation Council Secretary General Abdullatif al-Zayani.

Turkey, which has repeatedly called on Assad to step aside, is represented by Foreign Minister Ahmet Davutoglu while leading dissident, former premier Riad Hijab who defected in August, is also attending.

"We will discuss a structure that would unify the Syrian opposition," Hijab told reporters. "We are optimistic."

Also among delegates is Rima Flayhan, representing the Local Coordination Committees, made up of youth groups inside the country which have been at the vanguard of the uprising, as well as veteran opposition figure Haytham al-Maleh.

Long-time regime opponent who advocates peaceful change in Syria, Michel Kilo, however was not present but in a statement announced his support for the initiative.

The meeting began soon after the SNC announced it had during the night elected a new leadership, after being criticised for not being representative enough.

Some 400 SNC members had voted in a new Islamist-dominated 41-member general secretariat, which will now be tasked with electing 11 members to appoint a successor to its outgoing president Abdel Basset Sayda.

The process has been delayed until Friday to allow four members representing women and minorities to be added to the secretariat ahead of the vote, the officials said.

Before travelling to Doha on Wednesday, Arabi said that preparations must start for a transitional government to be ready when "there are changes on the ground" in Syria.

But in an indication it is reluctant to relinquish the cloak of leadership, the SNC has insisted that the "only body that can form a transitional government is a general national congress bringing together all political opposition forces, in which the SNC would hold the biggest share."

The SNC position appears to challenge an initiative proposed by prominent dissident Riad Seif, and reportedly backed by the United States, to unify the opposition.

Seif has reportedly proposed that the SNC be given only 15 of 50 seats in the new group, to make room for activists from inside Syria.

US Secretary of State Hillary Clinton last week called the SNC unrepresentative of opposition forces on the ground and said it "can no longer be viewed as the visible leader of the opposition."

The SNC -- which was set up six months after the uprising against the Assad regime erupted in March last year -- has in return accused Washington of undermining the revolt and "sowing the seeds of division."

The Syrian Observatory for Human Rights says more than 37,000 people have died since the uprising against Assad erupted in March 2011, first as a protest movement and then an armed rebellion after the regime cracked down on demonstrations.