moscow/geneva u.n. special envoy syria staffan de mistura say thursday would take part late round syrian peace talk kazakh capital astana friday month go hop break deadlock political talk geneva de mistura geneva peace process reach deadlock month miss say golden opportunity close almost seven years war blame intransigence side tell u.n. security council would start 2018 proposal involve wide constituency constitutional electoral reform since war side stick say thursday plan hold next round geneva second half january plan go astana meet de mistura say moscow start syrian talk russian foreign minister sergei lavrov russian defence minister sergei shoigu u.n. timetables routinely slip presence many global power elite world economic forum swiss resort davos jan. 23-26 could also create political momentum force loyal president bashar al-assad make big gain grind since russia join war late 2015 fight show sign end conclusively de mistura humanitarian adviser jan egeland say although few people siege reach humanitarian aid 2017 defy expectations bad 2016 many respect few aid convoy go december reach single soul besiege areas egeland tell reporters geneva hop astana might bring cessation hostilities rebel-held enclave eastern ghouta assad force besiege almost 400,000 people u.n. aid convoy wait syria government give green light food price rise eightfold since august egeland say 495 people priority list medical evacuations number go evacuate people die russia iran china egypt algeria iraq could bring influence bear say go get quagmire political agreements really hope astana meet next couple days kind impulse change humanitarian side u.n. join syria talk astana humanitarian hop