Macheda faces fierce competition for a place in United's first team, with Wayne Rooney and Javier Hernandez established as Sir Alex Ferguson's preferred partnership in attack.
Ferguson also has Dimitar Berbatov and Michael Owen at his disposal, while Danny Welbeck is also back at Old Trafford following his own loan spell.
Macheda spent the second half of last season on loan at Sampdoria but struggled to make an impact at the Serie A side, failing to score in 13 appearances, while the club were relegated.
The 19-year-old has already voiced his desire to remain at Old Trafford this season and fight for a place in Ferguson's line-up.
His agent, Giovanni Bia, says another loan spell with an Italian side is out of the question.
He told direttanews: "Federico is in Manchester and is very well in England. I rule out a return to Italy."
Macheda scored a double for United to help them beat New England Revolution 4-1 in a pre-season friendly last week.