"The Syrian National Council, which is the biggest bloc in the Coalition, has taken the firm decision... Not to go to Geneva, under the present circumstances (on the ground)," Council president George Sabra, told AFP.
"This means that we will not stay in the Coalition if it goes" to the peace talks in Geneva, he added.
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He invoked the ongoing suffering of Syrians on the ground and said his group would not negotiate before the fall of the regime.
The international community, led by Russia and the United States, has been pushing for the Syrian regime and rebels to attend a peace conference dubbed Geneva 2 to find a political solution to the conflict.
The proposed meeting has been delayed for months, but Washington and Moscow are now talking about a potential mid-November date for the talks.
The Syrian National Council has long said it will not negotiate until President Bashar al-Assad's regime is toppled.