Rasmus Hojlund may not play for Man United again after he was an unused substitute against Fiorentina on the day Benjamin Sesko signed.
United are confident a deal can be struck with Milan, who are rebuilding their squad following the return of coach Massimiliano Allegri. Milan finished eighth last season and failed to qualify for Europe.
It remains unclear whether a permanent deal could materialise as United value Hojlund at around £30million and Milan are seeking a loan move for the 22-year-old.
Hojlund is only two years into a five-year deal at United but the club decided early this calendar year to cash in if they recruited a new centre forward.
Benjamin Sesko was introduced to the Old Trafford crowd ahead of the pre-season friendly with Fiorentina on Saturday after he completed his £73.62m move from RB Leipzig.
Hojlund was an unused substitute in the 1-1 draw - the first time he did not appear in any of United's five pre-season matches. Head coach Ruben Amorim elected to start playmaker Mason Mount up front, having played Matheus Cunha there in the 2-2 draw with Everton six days earlier.
The MEN revealed last week sources close to Hojlund felt he would have to leave if Sesko came in. Hojlund is unhappy at United seemingly forcing him out and stressed only 12 days ago that he wanted to remain at the club. Amorim refused to give public assurances that Hojlund would stay.
International players are under more pressure to ensure they have regular playing time this season ahead of the 2026 World Cup. Hojlund has scored one goal in his past 16 appearances for Denmark and was dropped to the bench for their last qualifier against Lithuania.
United signed Hojlund from Atalanta in a £72m deal in July 2023, having planned not to break the £60m barrier for their new frontman. Hojlund has scored 26 goals in 95 games for the club.
Milan would provide familiar territory for Hojlund as the city is located around 40 kilometres from Bergamo, where Atalanta are based.