It is the second time since the end of the season that United have been rebuffed in their efforts to sign a five-star striker after being told Dimitar Berbatov will not be leaving Tottenham.
Kia Joorabchian, who was behind Tevez's transfer from Corinthians to West Ham last summer, has already spoken to officials at Inter.
They are prepared to pay up to £30m for Tevez and offer the player a four-year deal worth around £75,000-a-week and United won't be drawn into an auction.
Joorabchian said: "Of the English clubs, United are favourites because Carlos would like to go there - but if they want him, he will cost no less than £40m.
"After what they paid for the two Portuguese players and the price of Shevchenko a year ago, that has to be his value.
"He has proved himself in the Premiership - unlike Shevchenko - and is better and more experienced than the Portuguese boys."
