The 28-year-old Serbian international has been strongly linked with a move away from Old Trafford for the last year and has been a long-term target for Real Madrid and both Milan clubs.
But Vidic's representative, Silvano Martino, confirmed the Spanish giants were yet to register their interest in the Red Devils' centre-back but hinted that he was open to offers.
"Real Madrid? So far the Spanish club has not contacted us," Martino told Itasportpress.it.
"The player is on holiday in Mallorca and he is thinking about next season with Manchester United.
"It is difficult for him to leave England, even if with the market open anything can happen."
United are currently on a pre-season tour of America and manager Sir Alex Ferguson failed to dampen the speculation that Vidic could be on his way out when quizzed on the issue.
Speaking about the Serbian’s future after Manchester United’s 1-0 victory over Philadelphia Union on Thursday, Ferguson said:
“I couldn’t clarify that at all,” and he only went as far to say "I believe so" when asked if the Vidic would start the season at Old Trafford.
However, Vidic - who has continually had to deny reports that his wife Ana struggles with the gloomy weather in Manchester since moving from Spartak Moscow in 2006 - is due to join up with the rest of the squad next week when he returns from holiday and reports suggest United officials could be about to open negotiations on a contract extension.
With two years remaining on his current contract, United hope to end speculation by offering the dominant centre-half a two-year extension worth around £90,000 per week.
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