Sanchez arrived in Milan on Wednesday and underwent medical tests ahead of sealing a loan move to the 18-time Serie A winners.
The deal does not include an option to buy, which means, if Sanchez were to rediscover his form in Italy, United could demand a bigger fee for the Chile international at the end of his loan.
Sanchez, who joined United from Arsenal in a swap deal involving Henrikh Mkhitaryan in January 2018, has scored five goals in 45 appearances since moving to Old Trafford.
United were without Sanchez during pre-season because he was representing Chile at the Copa America. He scored twice in six games at the tournament held in Brazil as his country secured a fourth-placed finish.
Last modified on Friday, 30 August 2019