The 17-year-old is set to arrive in Manchester this weekend.
Adu told the Daily Express: “To go to one of the world’s biggest clubs and get a chance to train is an honour and a privilege.
“Cristiano Ronaldo and Wayne Rooney are two of my favourite players and getting the chance to train with them will be unbelievable.
“Hopefully this will lead to an offer in January or in the summer transfer window next year.
“That would be awesome.
“I hope I can show flashes of the kind of player I can become.”