beirut former al qaeda branch syria pledge keep fight government force russian iranian ally denounce ceasefire talk kazakhstan russia iran turkey agree friday deploy observers edge de-escalation zone syria idlib province largely control islamist insurgents hail agreement breakthrough months talk kazakh capital astana give detail move fall broad deal would set four zone across syria de-escalation plan ease fight part western syria rebel factions government force loyal president bashar al-assad ex-nusra front say astana process amount surrender rebel-held pocket start ceasefire would end restore bashar rule areas group cut tie al-qaeda last year rebranded spearhead tahrir al-sham jihadist alliance control part northwestern idlib province border turkey least two million people live idlib large populate area hold rebel include nationalist free syrian army factions take part astana talk idlib population balloon thousands civilians fighters leave areas syrian army seize help russian jet iran-backed militias tahrir al-sham criticize fsa rebel attend astana meet begin moscow-led diplomatic efforts separate u.n.-based peace talk geneva fear day come factions line alongside russian warplanes fight reject assad regime say statement bouthaina shaaban senior aide assad say friday attempt divide syria fail repeat government vow take back entire country include idlib areas assad gain military upper hand array rebel group include receive back unite state turkey gulf monarchies damascus view presence turkish force illegitimate syrian state news agency sana cite foreign ministry source say saturday deal idlib temporary main goal revive old damascus-hama-aleppo road ... kinds traffic flow aleppo source say government take full control aleppo city east idlib last year major blow rebel critics describe de-escalation plan de facto partition syria years multi-sided conflict moscow tehran ankara deny say zone temporary although could extend beyond initial six-month term ex-nusra vow fight syria denounce de-escalation deal