BEIRUT - Syrian opposition groups said on Thursday they would not accept a political transition plan proposed by international envoy Kofi Annan unless it explicitly required President Bashar Assad to step down ahead of the formation of a unity government.

According to diplomatic sources at the United Nations, Annan's proposal, aimed at ending the 16-month conflict in Syria, does not stipulate Assad's resignation, although it does say the unity government could not include figures who jeopardize stability.

"The proposal is still murky to us but I can tell you that if it does not clearly state that Assad must step down, it will be unacceptable to us," said Samir Nashar, an executive member of the international Syrian National Council.

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