David Sullivan wants Birmingham's future resolved by the end of next month after claiming Carson Yeung's proposed takeover is "dragging on".
Yeung has clinched a 29.9% stake in the club and it was thought the Hong Kong businessman would eventually buy out co-owner Sullivan and club chairman David Gold.
Sullivan told the Birmingham Mail: "I have to admit that I am concerned that this is all dragging on too long. It is not in the best interests of the club.
"Mr Yeung is a very nice man, he is very enthusiastic and he clearly likes his football. He has got some great ideas to expand the club and the brand in China and the Far East.
"But I genuinely don't know whether he is going to see it through. When he was here, it seemed as if some days he definitely would, others you weren't so sure.
"I wouldn't think it is a publicity stunt for him because he has spent £15million already and he is doing an audit at the moment, which he needs to do to justify what he's bought to the Hong Kong stock market.
"Different countries have different rules and he might have a different way of doing things, I don't know enough about the Chinese psychology.
"But, for the sake of the club, it needs to be sorted out one way or the other. By the end of September we really do need to know."