The Citizens were supposed to take part in the eight-team competition that will feature East African giants like Singida United, Yanga SC and Simba from Tanzania, and Kenyan trio Gor Mahia, AFC Leopards and Nakuru All Stars.
The winners could get an opportunity to face English Premier League side Everton.
But the timing of the week-long event, which kicks off on June 3, proved problematic for City, according to club chairman John Comitis.
"No, we were unable to accept the invite because of the timing of the tournament," Comitis tells KickOff.com.
"Because it's in the middle of our break we can't get the players back in halfway through their rest. But we [were] supposed to go to Kenya and have a tournament in there.
"The winners of that possibly will play Everton, but unfortunately I don't think we can participate - we are still busy trying to organise our programme."