Syria's main Western-backed opposition coalition has announced that it will take part in peace talks with the government if certain conditions are met, including allowing aid workers access to besieged areas.
The Syrian National Coalition made public its decision in a statement released on Monday, after two days of talks in Istanbul.
U.S. Secretary of State John Kerry praised the announcement, saying the group's participation would be a "big step forward."
The group wants the government to guarantee the establishment of humanitarian corridors, the release of detainees and that the peace negotiations will result in a political transition in Syria.
Opposition members have long demanded that President Bashar al-Assad have no part in the transitional government that the United States and Russia want the two sides to agree on at the Geneva peace talks.
No date has been set for the proposed conference, which has been repeatedly delayed as U.S., Russian and U.N. diplomats struggle to get the two sides to agree to take part.
Coalition members want the backing of rebel fighting units, community leaders and activists inside Syria to counter criticism that they are out of touch with those battling on the ground.
Major Islamist rebel brigades have declared their opposition to the Geneva process if the conference does not result in Assad's removal. Some have said they would charge anyone who attended the planned international talks with treason.