geneva u.n. special envoy syria staffan de mistura urge russia wednesday convince ally syrian government need clinch peace deal end nearly seven-year-old war de mistura speak swiss television station rts say failure make peace quickly unite nations mediation could lead fragmentation syria russian president vladimir putin surprise visit monday russia hmeymim air base syria declare work russian force largely do back assad government militants follow defeat battle-hardened group international terrorists de mistura ask signal putin could give position force say convince syrian government time lose .... think win territory militarily win peace win peace courage push government accept new constitution new elections unite nations say nearly seven-year civil war syria kill hundreds thousands people drive 11 million home previous diplomatic efforts resolve conflict end failure opposition demand president bashar al-assad leave power refusal go kremlin first launch air strike syria september 2015 big middle east intervention decades turn tide conflict assad favor regard mission complete putin want help broke peace deal keen organize special event russia syrian congress national dialogue moscow hop bring together syrian government opposition try hammer new constitution de mistura make clear peace negotiations must unite nations geneva mandate u.n. security council add otherwise worth .... complicate war geneva u.n. u.n. envoy conduct shuttle diplomacy syrian government delegation lead chief negotiator bashar al-ja afari unify opposition delegation opposition tell clearly arrive yesterday morning ready meet government right away hard difficult discussion government ready say ready meet opposition regrettable diplomacy many mean de mistura say senior western diplomat say government delegation fail engage de mistura new constitution elections round negotiations due end thursday clearly intention engage political process clearly sufficient pressure diplomat tell reuters clear impression regime want avoid u.n.-led political process cost putin must nudge syria u.n. peace deal mediator say