The Brazilian attacker was one of the stars of the recent U-17 World Cup, alerting a whole host of European clubs in the process.
Chelsea have been one of the more interested parties, and have been watching the teenager closely in recent times.
United are also keen, but the Blues may move early to tie up a deal.
Atletico Paranaense are aware that they may struggle to keep their wonderkid, with a £4m valuation said to have been placed upon him.
The London club can easily match this figure, but will have to wait until next month when Mosquito turns 18 before they can secure an agreement, due to strict rules in Brazilian football.
If signed, the forward would likely be loaned out to feeder club Vitesse Arnhem to gain experience, before being brought back in the future to compete for a first-team berth.
United could yet move to beat their domestic rivals, but with more established names needed at Old Trafford to ease growing concerns they may opt against a move.
Real Madrid and Juventus are also keen.