UNITED have been put on red alert after reports in Spain claimed Nemanja Vidic is eyeing a move to Barcelona. The Serbian interntional's agent, Paolo Fabbri, was reported as saying it was Vidic's dream to move to the European Champions. He has since denied the claims, but it is yet more unwanted speculation about the 27-year-old's future. Vidic has been linked with moves to Barca and Inter Milan in the last six months, but Sir Alex Ferguson has so far resisted any attempts to lure him from Old Trafford. And after losing Cristiano Ronaldo and Carlos Tevez this summer, the United boss will not welcome more speculation about another one of his stars. Fabbri is reported to have told Radio Catalunya: "It would be a dream for Vidic to play for Barcelona as he wants to play in La Liga. Decision ?But if we are realistic United have just lost Cristiano Ronaldo and Carlos Tevez and don't want to lose another key player.? He has since denied the comments, saying: "Nemanja is happy in Manchester. If Barcelona do make an offer for him then it is up to United to make a decision." Vidic has been a resounding success since moving to United in 2006 in a £7m deal from Spartak Moscow. But he has made it clear that he has struggled to settle in Manchester, with his wife, Ana, keen to live elsewhere. Barcelona would be his preferred destination, but any suggestion that he wants to leave United would spark a clamour from Europe's top clubs. Though Ferguson will not sanction a move this summer, he could be ready to do business at the end of the season, particularly with the emergence of Jonny Evans at the heart of United's defence.