The Chilean International has completed his medical at Carrington and has made his way to Old Trafford on Monday morning where he was greeted by Sir Alex Ferguson.
The only thing left to do now is for United to announce the deal officially.
But if reports are to believed then the announcement could still take some more time.
According to sports journalist Mark Cardenas, Manchester United will only announce Alexis Sanchez once Arsenal confirm Henrikh Mkhitaryan.
Cardenas tweeted: “United will make the announcement of Alexis once Arsenal confirm to Mkhitaryan first.”
El United hará el anuncio de Alexis luego de que el Arsenal confirme a Mkhitaryan primero.
— Maks Cárdenas (@MaksCardenas) January 22, 2018
Henrikh Mkhitaryan is scheduled to have his medical at Arsenal on Monday and if Cardenas is right then United will announce their signing only when Mkhitaryan completes his medical for the Gunners.