The 21-year-old has made just three appearances for the Red Devils this season, none of which has come in the Premier League.
"We are at an advanced point with Stuttgart," Giovanni Bia told Tuttomercatoweb.com. "Negotiations are going well but he is a player who is liked by a lot of clubs. Two Spanish ones, for example, are looking to intervene.
"There are Italian sides, too, from Siena to Bologna and others, but I think that [United manager] Sir Alex Ferguson wants to send him to a foreign side outside of the peninsula.
"He'll join a club on loan with the option to be signed outright as his contract expires in June 2014."
Macheda himself said earlier this week that he is open to moving out of Old Trafford on loan for the remainder of the season.