Manchester United are believed to be stepping up their pursuit of Atletico Madrid striker Sergio Aguero amid speculation that the Premier League champions have already had a €46million (£39.5m) bid rejected for the Argentine wonderkid.

United boss Sir Alex Ferguson is understood to have identified the 21-year-old hitman as the 'crown jewel' of his summer rebuilding plans at Old Trafford having lost Cristiano Ronaldo to Real Madrid and Carlos Tevez, who is expected to sign for neighbours Manchester City.

According to Spanish daily AS, Ferguson is willing to offer a number of proposals in an attempt to convince Los Colchoneros to sell their prized asset, who hs been a revelation in the Spanish capital since joining from Independiente for a reported €23million (£19.7m) in 2006.

The first of which is said to be his preferred option and includes Portuguese winger Nani, who has been a disappointment at the Theatre of Dreams since his move from Sporting Lisbon in 2007, and a payment of €40million (£34.3m).

But with Atletico already well stocked in the wide areas, the second option may well be the most likely with AS reporting that 'Fergie' is willing to offer €20million (£22.1m) plus Bulgarian striker Dimitar Berbatov, who supposedly fancies a move to the Vicente Calderon after struggling for form since his summer move from Tottenham.

Although this offer would certainly appeal to Atletico president Enrique Cerezo who has previously stated that they would consider selling Aguero if an "interesting offer" was made - which United's one certainly is - the Spanish club have publicly declared recently that the player is not for sale and will only leave if a side is willing to meet his €60million (£51.5m) buy-out clause.