However, he would be a major boost to O'Neill's midfield options in the short-term. The Wearsiders have held productive talks with the MLS club, says The Journal.
Cahill is apparently keen on a deal which would extend until February before the player returned to America for the start of a new season across the Atlantic. Such a deal is a situation the Black Cats boss would be happy to facilitate.
He said: "There are two things to it.
"One, if you felt a player was coming here who was going to be of value early but also can take the club along and improve the club I don't mind doing it. That I don't mind."