The 26-year-old was one of the top scorers in the Conference last season with 27 goals, and he spent a week training with Birmingham towards the end of the campaign.
However, a number of other clubs have since shown an interest with the likes of Blackburn, Sheffield United and Hibernian all keen.
However, it appears that Lee Clark is set to land his man with Green set to undergo a medical with Birmingham on Wednesday - after which he is scheduled to put pen to paper.
Mansfield boss Paul Cox has already accepted that Green would be leaving Field Mill, despite their promotion back to the Football League.
"Judging by how he has been talking, he is likely to sign for Birmingham," said Cox.
"Birmingham have put an offer in front of him and they are still talking. I am not sure if Matt has accepted it or not. Matt wants to play in the Championship.
"We made a very good offer, but I think it is more down to ambition rather than the financial aspect.
"He has (also) spoken to a number of League One clubs, but he said if he doesn't sign for Birmingham he will come back here."