The Colombian midfielder had been on the verge of joining Juventus in January, then extended his contract in March, but remains on the fringes of the squad.
According to Sportmediaset and Tuttosport, Inter are particularly eager to send Guarin to Manchester United, knowing they will pay more than Juve were offering.
The proposal will be put forward on Tuesday, as both clubs are in America for the Guinness International Champions Cup.
Manchester United want at least €15m (£12m) for 26-year-old Mexican striker Hernandez, which can be turned into a straight swap for Guarin.
The Colombian would be an alternative to Arturo Vidal, as Juventus have no intention of releasing the Chilean.
OUR VIEW: Obviously, United want Arturo Vidal but that is looking increasingly unlikely. So this deal could suit all parties. Hernandez is said to be unhappy at United so a switch to Italy would suit while United are hardly short of forwards and reinforcements in midfield are very much needed.
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- Sports & Recreation
- Manchester United
- Arturo Vidal