The 21-year-old, who has netted 42 league goals in 112 appearances for the rojiblancos since arriving from Independiente in 2006, had already been linked with a move to Chelsea and Inter Milan during the close-season.
And now fresh reports have suggested Premier League champions Manchester United are keen on acquiring the Argentina international's services as they attempt to find a replacement for Real Madrid-bound FIFA World Player of the Year Cristiano Ronaldo.
However, the Vicente Calderon outfit have already had to deal with transfer speculation linking their other goal-machine, Diego Forlan, with a move away from the club in recent months.
And club president Enrique Cerezo says he is confident of keeping hold of Aguero - who has netted six times in 18 outings for his country - as well.
"I know that the big clubs of Europe are interested in our player, but I have spoken with the people next to Kun and I am convinced that next season he will continue in the squad," he said.
While an Atletico spokesman added the club have received no offers for the forward.
"We have not received formally any offers and the club's board of directors have had a meeting and the decision is clear, Aguero is not for sale and only if a club pay his release clause could an exit be possible," he said.
The striker's release clause is believed to be in the region of £50 million.
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