through all the attempts at common ground. russia still won't accept syrian president assad's responsibility for the chemical attack, repeatedly insisting on a full investigation. the u.s.'s view -- >> the facts that we have are conclusive that the recent chemical weapons attack carried out in syria was planned and it was directed and executed by syrian regime forces. >> reporter: tillerson says assad's days are numbered. russia explained at length why ousting him could be disaster on the delicate issue of russia's interference in the u.s. election? >> as to the question of the interference with the election, it's well established in the united states. it's one that we know is serious enough to attract additional sanctions. >> reporter: lavrov called for more information. >> translator: not a single fact has been confirmed who saw those facts.