Syria's internationally recognised opposition group has approved nine "ministers" for an interim government charged with running Syrian territory that is in rebel hands.
The move by the National Coalition late on Monday followed its announcement earlier in the day that it planned to attend proposed peace talks with the Syrian government, if certain conditions were met.
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It also stipulated that President "Bashar al-Assad and those with the blood of Syrians on their hands have no role in the transitional phase and Syria's future".
In a statement issued after two days of meetings in the Turkish city of Istanbul, the National Coalition said it would take part in the Geneva peace talks only if humanitarian aid is allowed to reach besieged areas and the government releases political prisoners.
"Whether or not to go to Geneva is the decision of the Syrian people," Louay Safi, a member and spokesman of the National Council, said in a statement on Sunday.
"The Coalition is nothing but a mechanism to apply their will."
The National Coalition has struggled for months to cobble together an interim government, in part because of infighting among the various exile groups involved, ranging from secular intellectuals to Islamist activists.
Western leaders have expressed encouragement following the National Coalition's inclination to take part in the Geneva talks.
Speaking in Abu Dhabi, John Kerry, US secretary of state, said any decision by the opposition to take part in talks would be a "big step."
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"We take note of the fact that ... the Syrian opposition voted to go to the Geneva II [conference]. This is a big step forward and a significant one," he said.
For his part, William Hague, British foreign secretary, told parliament MPs "I strongly welcome" the opposition's readiness to attend the talks.
But the proposed Geneva conference faces a series of obstacles: the most powerful and best-armed rebel groups are not party to the talks, and most fighting units are disorganised bands with little central command or leadership.
The coalition's already slim support inside Syria received a severe blow in September when nearly a dozen of the most powerful rebel factions publicly broke with the coalition.
Even if an agreement is reached in the Swiss city, it is unclear if it will be accepted on the ground. As diplomats have been trying to convene peace talks, the fighting on the ground has raged on.
The brigades said they do not recognise any government formed outside Syria.
While the opposition's talks in Turkey were taking place, government forces took over the town of Tel Aran and other positions in the northern province of Aleppo, state media said.
The attack on Aleppo came a day after Assad's forces consolidated control of a key military base held by rebels since February, part of a steadily advancing offensive that has reversed rebel gains in recent weeks.
The British-based Syrian Observatory for Human Rights and an Aleppo activist said they believed the government's gains were partly caused by rebel infighting.
The Observatory, which receives its information from a network of activists on the ground, also reported the government advances.
The al-Qaeda-linked Islamic State in Iraq and the Levant in particular, they said, was trying to drive weaker opposition groups from rebel-held areas.