The 33-year-old striker has been told by officials at St Andrew's that he is free to talk to other teams ahead of transfer deadline day.
"Marlon's situation hasn't changed. He has been given a free, which was confirmed to him two or three days after the season had finished," Clark told the Birmingham Mail.
"He has been given time off to pursue other opportunities. He is talking to them with his agent, with my permission, and has been over the last couple of weeks, we expect a conclusion in the coming days."
King joined Birmingham from Coventry City in 2011.