The Mail on Sunday says the son-in-law of Diego Maradona has a £50million buy-out clause in his contract with Atletico Madrid, who might be persuaded to accept £35m.
But Argentina coach Maradona is urging him to join Inter Milan at the end of the season, which would not disrupt his World Cup preparations.
Atletico could extract the maximum price from Chelsea in January, with it potentially being the London club's last transfer until June 2011. But delaying any sale to the summer might pacify unhappy fans.
An added problem is the incoming 50 per cent tax rate in the UK. Aguero currently earns £4.5m a year net in Spain, although that will be affected by the change in Spanish tax laws that come into effect on January 1st.