The Red Devils have been linked with the Portuguese ace for some time, and are believed to have had scouts running final checks on the 21-year-old over weekend.
United boss David Moyes is rumoured to be keen to dip into the transfer market over the coming month, with a holding midfielder a priority.
The Angola-born ace has emerged as one of Portuguese football’s top talents in recent times, with his commanding displays alerting a host of top clubs from across the continent.
Sporting are far from willing to let one of their latest stars leave, but United are hopeful that they can negotiate a deal way below his £37.5m release clause.
The two clubs have conducted much business in the past, with Cristiano Ronaldo and Nani having both moved to Old Trafford from Lisbon.
Moyes is hoping that this relationship will once again work in his favour, with Carvalho being tipped to develop into one of European football’s top talents.
United are also being heavily linked with Atletico Madrid’s Koke.