Cameroon coach Winfried Schaefer has accused FIFA of "failing to respect African teams" by giving group E rivals Germany preference in a mix-up over training times.
The German-born Schaefer was furious after learning his African champions could not train at 1900 local time on Monday because their schedule clashed with the three times winners.
"This is a prime example of FIFA and (Japanese organising committee) JAWOC not respecting the Cameroon team and African teams in general.
"We are the home team and according to FIFA rules, we should choose when we want to train," Schaefer said.
"In the future, we need to make sure that African teams get the same treatment as bigger teams."
Team manager Andre Nguidgol told Reuters the "misunderstanding" was being sorted out and Cameroon would be able to train when they wanted.
"The general coordinator of Shizuoka is doing his best to rearrange the training. Cameroon will train at seven o'clock," he said.
Cameroon need to win the match to ensure second round qualification. They have four points from two games but an inferior goal difference to Germany who beat Saudi Arabia 8-0.
Both Germany and Cameroon drew with Ireland 1-1 who can also progress if they beat Saudi Arabia.