that is really for the ukrainians to speak to, not the u.s. military. i know of no involvement of us in respect to that. >> president biden said that the u.s. will join allies to close the u.s. air space to russian planes. the civilian aviation course, we know that the u.s. military has part of civilian air space under its control and russian military and cargo planes cross into that air space from time to time. any plan to employment russian military assets in northern syria where the u.s. air force controls? >> i'm not aware of any such plans. as you know, we are in syria for one purpose and one purpose only and that is to counter the isis fight and that remains an active fight. and there is a deconfliction mechanism with russian military