Sanchez's future has been the subject of intense speculation in recent weeks, with United seemingly beating off competition from local rivals and Premier League leaders Manchester City for the 29-year-old's signature.
The deal, which will also see Henrikh Mkhitaryan move in the opposite direction, is expected to be announced in the next 24 hours, and the first photo of Sanchez in a United shirt has now apparently been released.
BREAKING: Alexis Sanchez in a Manchester United kit. pic.twitter.com/FYvkl6IKnS— FourFourTweet (@FourFourTweet) January 21, 2018
Sanchez could make his debut for United when they take on Yeovil Town in the FA Cup fourth round on Friday night.