Dave Thompson/Associated Press
The Sun's Neil Ashton exclusively reported as much, with the Argentinian unhappy at playing second fiddle to Gabriel Jesus at the Etihad Stadium and eager to join Los Blancos at the end of the season.
The Spanish side are equally keen but will need to fork out "over £60 million before City even consider selling Aguero to a [UEFA] Champions League rival."
Aguero's position at City has come under threat since the arrival of Jesus in January, with the Argentinian initially sidelined in favour of the Brazilian.