Maybe ask him for some help, letting him know that a friend has offered help if he "isn't able" to help you. That way he knows he is needed and his ego is built, but he also knows that if he chooses not to help you, you will be ok - but someone else will be there to fill his place.
As long as this doesn't come across as an ultimatum, I don't see the harm. But you know your own situation!
