Mouaz al-Khatib, a former imam, has been selected to head the newly-formed Syrian National Coalition, a delegate has revealed.
Riad Seif, an influential businessman who proposed the US-backed initiative to set up the umbrella organisation joining opposition groups inside and outside the nation, was elected as deputy president on Sunday.
Suhair al-Atassi, a well-known female activist, was elected as the second deputy president.
The unity deal, signed at a meeting in Qatar, was described as a hard-won victory for the Syrian opposition in the fight against Bashar al-Assad, Syrian president.
"We signed a 12-point agreement to establish a coalition," Riad Seif said.
Participants in marathon talks in Doha said discussions were continuing on details of a planned new government-in-waiting, but that the Syrian National Council had now heeded Arab and Western calls to join a new, wider coalition.
Reservations in SNC ranks about what many members saw as a move to sideline them had prompted repeated delays in the Doha talks.
But after negotiations that ran into the early hours of Sunday and resumed in the afternoon, opposition officials said a deal had finally been reached.
'An advanced step'
Al Jazeera's Mohamed Vall, reporting from Doha, said that the key players were still working out the details.
"We also know that this name: the Syrian National Coalition will also change because they do not want it to sound like Syrian National Council when reduced to its acronym of SNC.
"There is also a longer version of the name, which is: The National Coalition of the Syrian Revolutionary Forces and the Opposition".
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Our correspondent said that the Kurdish National Council asked for 48 hours to consult with their leaders outside of Qatar, but all indications were that they "were going to sign this paper".
The deal came after the Syrian National Council, which had formerly been seen as the main representative of the opposition, heeded Arab and Western pressure to agree to a new structure embracing groups that had been unwilling
to join its ranks.
Al Jazeera's Hashem Ahelbarra reported that the coalition had said that as soon as they received "full recognition from the international community, they will announce a provisional government".
"Ideally they say they will ask the international community to provide them with a humanitarian corridor, a no-fly zone in the northern parts of the country, preferably in Idlib province or in Aleppo, but they say that they practically need a month or two before being able to move to that area, to set up their provisional government," our correspondent in Doha said.
Speaking after the agreement was signed and announced, Qatar's Prime Minister Sheikh Hamad bin Jassim said: "This work has ended but the next step is more important".
The Qatari PM said that the new umbrella group should be recognised as the only legitimate representative of the Syrian people.
"Trust us that we will strive from now on to have this new body recognised completely by all parties ... as the sole legitimate representative of the Syrian people," he told reporters.
Meanwhile, Ahmed Davutoglu, Turkish foreign minister, said the opposition was no longer divided and needed full backing.
"The friends of Syria ... should support this agreement ... There is no excuse anymore," he said.
"All those who support the rightful struggle of the Syrian people should declare clear support for this agreement and be more active."
The 10-member transitional government would be elected by a new 60-member umbrella group to be drawn from civilian activists and rebel fighters inside Syria, as well as by the exiles who have dominated the SNC.Mouaz al-Khatib, voted in as the first leader of this coalition of unified opposition, is a former imam at the famous Umayyad mosque in Damascus.
He was imprisoned several times for criticising Assad's rule before he left Syria for Cairo this year.
Delegates said he had been the only candidate for the post of president.
"He is from Damascus and is a famous man from there. I think this is a serious step against the regime, and a serious step towards freedom," Syrian National Council leader George Sabra said. He also praised the choices of Seif and Atassi.
"They are very good representatives of this project. They are activists in our revolution. Most of them have made large
sacrifices for the people inside the country."
Former prime minister Riad Hijab, who fled to neighbouring Jordan in August in the highest-ranking defection from President Assad's government, hailed the agreement as "an advanced step towards toppling the regime".