Syria's main opposition grouping said Monday it will attend peace talks on the condition that President Bashar al-Assad transfers power and is excluded from any transition process.
In a statement issued after two days of meetings in Istanbul, the key National Coalition said it would take part in mooted peace talks in Geneva "on the basis of the full transfer of power."
It also stipulated "that Bashar al-Assad and those with the blood of Syrians on their hands have no role in the transitional phase and Syria's future.
Speaking in Abu Dhabi, US Secretary of State John Kerry said any decision by the opposition to take part in talks would be a "big step."
"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," Kerry said.
British Foreign Secretary William Hague told parliament MPs "I strongly welcome" the opposition's readiness to attend the talks.
"We continue to push for a date for a peace conference to be agreed, and UN and Arab League Envoy Lakhdar Brahimi has reiterated that he is still trying to convene a conference before the end of the year," he said.
Syrian opposition figures have long said that Assad should have no role in any political transition process, insisting he must step down.
But the Syrian government, while expressing willingness to attend the proposed Geneva conference, insists that Assad's departure from power is not up for discussion.
Monday's statement, issued by the Coalition's General Assembly, also calls for the establishment of humanitarian aid corridors and for the release of prisoners.
"The Coalition also requires that prior to the conference, aid convoys from the Red Cross and Red Crescent and other aid groups be granted continued access to besieged areas," the statement said.
And it demands "the release of detainees, especially women and children," without providing additional details.
The international community, led by the United States and Russia, have been seeking for months to convene a Syria peace conference in Geneva.
But proposed dates for the conference have come and gone with no progress towards talks.
The Syrian National Council, a key Coalition member, has previously threatened to leave the umbrella grouping if if some of its members agree to attend Geneva talks.
But Monzer Aqbiq, an advisor to Coalition president Ahmed Jarba, said Monday that the Council appeared to have changed their mind.
"The resolution has been approved quasi-unanimously," he said of the statement released on Monday.
"They have obviously changed their mind because they voted yes for the text."
Aqbiq said persuasion and explanation of the goal of the talks had helped convince some sceptics.
"There are many groups that when you're explaining to them that political transition means that the regime will change, they immediately know how it is and say OK," he added.
But the gaps in the consensus Aqbiq described were already clear.
"Whether or not to go to Geneva is the decision of the Syrian people," said Louay Safi, a member of the Syrian National Council and a spokesman for the Coalition, in a statement on Sunday.
"The Coalition is nothing but a mechanism to apply their will."
The opposition wrapped up its Istanbul meeting late Monday by nominating nine "ministers" for an interim government charged with running Syrian territory in rebel hands.