under the agreement hashed out between russian form minister sphrofsergey lavrov and secretaf state john kerry. >> to that end we have also established a task force under the auspices of the u.n. and co-chaired by russia and the united states. over the coming week, this group will work to develop the modalities for a long term comprehensive and durable cessation of violence and hostilities. >> reporter: both sides have already gra agreed that i.s.i.l. and the el nusra front are legitimate targets, the pentagon says any eventual assess fire. >> there is no fire for us to assess. wcease. we continue to operate against i.s.i.l, those will continue because those are not groups did that are party to the ceasefire. >> the u.s. says focused on rebel groups that are opposed to be assad regime. aleppo where i.s.i.l. isn't operating. so a lot rides on who is labeled a terrorist. >> translator: well, if liberation of the city that has been taken by legal armed groups can be qualified as aggression well then, probably. >> reporter: russia says it welcomes cooperation by the united states, while the