However, United chief executive David Gill has now revealed that Manucho has now automatically qualified for a work permit and can now play for United.
"We couldn't get a work permit for him straight away, but when we looked at the rules and regulations we found that he actually qualified for one automatically. We're delighted to have him," Gill told MUTV.
"He's 25 years-old and has got a lot of great attributes.
"You only need to look at the goals he scored at the African Nations Cup to see that and I think he brings something different to the team.
"He's got a little injury at the moment, but we're looking forward to him getting fit and showing us what he can do. He's a great prospect."