That's according to Spanish pundit Guillem Balague.
He wrote on Twitter: "Alexis Sanchez not fully agreed yet. United favourites and next 2-3 days key (nobody takes City out of equation yet). Meanwhile Arsenal want to close soon deal for Aubameyang, left out of squad today, for €60m (£53m)."
The Gabon international was left out for 'disciplinary reasons'.
Dortmund boss Peter Stoger told Sky Germany: "He hinted briefly that he had forgotten the appointment, but the meeting was announced everywhere and several times.
"But anyone who knows me is aware that I am not vindictive. He can be back in action next week.