I have difficulties communicating other people's mistakes/shortcomings.
The most common time this happens to me is when my department head assigns me with supervising a project to deadline, but my direct line manager is responsible for executing some of the most vital tasks of the project - and he postpones them significantly.
So for example, we have to finish Project X by Friday, and all the sub-tasks I and my assistants have to do are done long before that. But there's a final sub-task (a bit like a "big red button") which only my line manager can perform. And he can't because he has other priorities.
So when our department head asks me, I feel stuck firstly because I don't know what they have discussed among themselves already, and secondly also because I don't want to sound like I am accusing my line manager.
I am in part afraid to cause pressure on my direct line manager most importantly because he is, well, my day-to-day boss and influences my career growth, my workplace, my everything every day. It is also very difficult to get specific dates from him, as his schedule changes all the time. He never gives clear answers to me.
So I literally get stuck, am like "ahem... errm... I have to check... I am not sure..." whenever this happens.
Would it be possible to say something like "I have done my part way ahead of schedule. I am waiting for my boss to be free. He usually needs an entire day to focus on something like this."?