The leader of the Free Syrian Army said that rebel militants loyal to him would not halt fighting during a planned peace conference in Switzerland in January.
General Salim Idriss told the Arab television news channel al-Jazeera that rebels would instead continue their fight to topple President Bashar al-Assad during the talks.
"Conditions are not suitable for running the Geneva 2 talks at the given date, and we, as a military and revolutionary force, will not participate in the conference."
"We will not stop combat at all during the Geneva conference or after it, and what concerns us is getting needed weapons for our fighters," he continued.
The Syrian government and opposition forces are set to convene in Geneva on 22 January next year.
United Nations Secretary-General Ban Ki-moon said that it would be "unforgivable not to seize this opportunity to bring an end to the suffering and destruction."
Optimism surrounding a breakthrough in the Syrian civil war has grown after world powers struck a deal with Iran on Sunday to roll back aspects of its nuclear programme.
More to follow.