"We have accepted Birmingham's offer and Stern is now traveling to the West Midlands to talk to them," Forest manager Paul Hart told the club's official website.
The international striker would have been available on a free transfer this summer when his current contract expires, but it seems cash-strapped Forest are prepared to cash in on their prize asset.
Blues boss Steve Bruce will be hoping to wrap up the deal in time for John to play some part in Saturday's clash with Crewe at St. Andrew's.