The Red Devils have made the German international their top target for the summer, with David Moyes desperate to rejuvenate his struggling squad.
But, the likes of Real Madrid and Arsenal have also been linked with the 23-year-old in recent times.
However, United are growing increasingly confident that a £25m swoop will be pushed through later this year.
Much depends on Gundogan’s ability to recover from a troublesome back injury, which he is expected to bounce back from.
A possible deal could be sealed using straight cash, or Shinji Kagawa may be a makeweight.
The Japanese playmaker signed for United from Dortmund in 2012, and is still a favourite at the Bundesliga club.
The Premier League champions may also push for Bayern Munich’s Toni Kroos as they plot a midfield overhaul.
The playmaker is another realistic target, with his contractual situation at the Allianz Arena far from clear.
Kroos is not short of admirers, with Manchester City and Liverpool having been linked with him.