Valencia have reportedly offered £17m plus veteran defender Roberto Ayala for Cristiano Ronaldo.
The Manchester Evening News say that the Spanish club have launched the 'cheeky bid' but Man United are unlikely to be swayed by the offer of a 33-year-old centre-half as a makeweight in the deal.
Ronaldo has made no secret of his desire to leave the club after being villified for his part in Wayne Rooney's sending-off during this summer's World Cup.
Real Madrid have been strongly linked with a move for Ronaldo, but there have been no firm offers from the Spanish giants.
AC Milan coach Carlo Ancelotti has meanwhile ruled out a move for the Portuguese star, saying: "Cristiano Ronaldo? He's a guy with good qualities. But he's a winger and so he can't play at Milan. We would have to change our game."
United unveiled Michae Carrick on Wednesday and are very close to making their second signing of the summer, Villarreal anchor man Marcos Senna edging towards a £3.4m move in the next few days.