The full-back has been training with the Tannadice club this summer after being released by Bristol City, performing well enough in sessions to invite discussions over his willingness to sign.
The defender was a favourite of United supporters before earning a move to Celtic in 2006, although persistent trouble with his knees punctuated his time in Glasgow. A spell at Bristol was also less than fruitful.
"We're trying to tie Mark up short-term. It's for six months," said Jackie McNamara, the United manager. "He's down south just now but we're speaking to him again tomorrow with a view to doing something. Mark had a good connection with the club before and it's important he gets back playing."
Gavin Gunning will be made to serve time out of the side, though, after United confirmed that they will not appeal the red card he was given during a draw with Hibernian on Saturday. The defender was involved in a scuffle with Hibs' Kevin Thomson midway through the second half - an incident which caused both players to be dismissed.
However, the Easter Road club last stated that they will appeal against the decision to send off Thomson. The club's conviction of his innocence is so strong that Hibs have spent £1000 to fight his corner.