Darlington boss Dave Penney called for a swift conclusion to the ongoing transfer saga for the 23 year old.
He told the Aberdeen Press & Journal: "If the deal isn't done next week, we will pull it and Tommy will stay with us."
Dons boss Jimmy Calderwood remains confident, saying: "We are hoping to get Tommy up on Sunday or Monday. The first thing is to get him through the medical and go from there.
"He will be a good addition. He has a determination to succeed here and he will need that because it will not be easy to adapt to the Scottish game."