Gray, who played under Addicks boss Iain Dowie during his time as manager of Crystal Palace, has fallen out of favour at St Andrew's and may welcome a move back to the Capital to kick-start his career.
Media reports over the weekend suggested a possible swap deal with Addicks striker Marcus Bent moving in the opposite direction.
Birmingham manager Steve Bruce is a big admirer of Bent and is said to be keen to add to his strikeforce after learning that Mikael Forssell is sidelined for three months.
