Making it clear that you have no romantic feelings for him should prevent any confusion and make it easier for him to get over his disappointment.
ان قولك بوضوح انك لا تملكين اية مشاعر رومنطيقية تجاهه سيجنّبه التشويش وسيسهِّل عليه التغلُّب على خيبة امله .‏