The Red Devils were linked with a move for the commanding Colombian last month, but an agreement was not reached despite rumours of a possible swap deal involving Javier Hernandez.
Yet David Moyes has maintained an interest in the 27-year-old ahead of the summer.
The Scot is said to be desperate to invest in his ailing squad when the next transfer window opens in a bid to turn around their poor form.
Although signing a centre-back is seen a must, a dynamic and mobile central midfielder is a priority, with the likes of Tom Cleverley, Marouane Fellaini and Michael Carrick not seen as suitable.
Guarin is thought to be keen on a Premier League move, but Inter are looking to keep him at the San Siro.
They are said to be plotting a new contract offer, however if this is refused then a move away from Italy looks the most likely option.
Guarin – whose deal expires in 2016 – is aware of the interest, by may hold off making a decision until after the World Cup.