Premier League champions are set to enter the race for Porto's Brazilian midfielder Fernando, according to Portuguese newspaper A Bola.
The 26-year-old, who signed for Porto in 2007 from Brazilian outfit Vila Nova, is wanted by David Moyes to bolster the Red Devils' midfield options.
However, United face stiff competition for the former Brazil U20 star, with Italian giants Inter Milan and Juventus both reportedly keen.
United spent £27.5m on Belgian midfielder Marouane Fellaini at the end of the summer transfer window, but Moyes wants further reinforcements after a disappointing start to the 2013/14 Premier League campaign.
The former Everton boss also attempted to bring Athletic Bilbao's Ander Herrera to Old Trafford in the summer, but the Spain U23 international would cost over £30m, and United are not convinced the 24-year-old is worth the money.
Fernando, on the other hand, could be purchased relatively cheaply in January. The midfielder's contract expires next summer – and Porto will lose him for nothing unless they agree to sell this winter.
However, that is likely to depend on whether Porto reach the knockout stages of the Champions League.