Owen Coyle is believed to have resigned to losing the England international after the club accepted a bid of £7million fee from the Blues.
But the move has hit a snag after Cahill failed to agree personal terms with the London club.
Now according to The Sun newspaper, United are alerted of the situation and could launch a surprise bid to prise the highly-rated defender to Old Trafford.
With captain Nemanja Vidic out for the whole season and the rest of the defence struggling with injuries, United have suffered in form of late - losing back-to-back games including a 3-0 defeat to Newcastle on Wednesday.
Sir Alex Ferguson has previously insisted he would not spend in January unless the right player is available in the market.
Cahill could be the player United desperately need as they look to find a solution to their injury-hit defence and fading title hopes.