際に/際/際は => occasion, time N2
否定形 => Negative form N5
Conjugate verbs
予定だ => plan to, intend to N4
[際「さい」]して/に([際「さい」]し)/に[際「さい」]しての => At the time of A (which starts now).. N2
Time, Situation
に際して => on the occasion of; at the time of ~ N2