The 23-year-old Argentina international was at City's Carrington training ground on Wednesday morning having cut short a holiday in his homeland to fly in to finalise contract negotiations and undergo a medical. Aguero, the son-in-law of Diego Maradona, is currently on leave having been involved in the Copa America.
"Just arrived in Manchester to finalise the details of signing with City," Aguero wrote on Twitter.
"Everything is going very well! I'll tell you more in a while."
With striker Carlos Tevez adamant he wants to leave City to be nearer his family in Argentina, Aguero is seen as the ideal replacement.
Younger than his compatriot by four years, the Atletico Madrid star has been a prolific goalscorer in La Liga. He is one of the most sought-after strikers in Europe, which is why his club inserted a ?£38million buy-out clause when they gave him a new contract in January.
Atletico had resigned themselves to the fact they would lose their prized asset when he announced in May, before the Copa America, that he wanted to leave. Aguero's preference was to remain in Spain, with city rivals Real seemingly the most likely destination, but Atletico were keen to resist such a move.
So for Atletico an offer from Manchester City, although Italian club Juventus were also interested, represented the preferred option.
Atletico coach Gregorio Manzano admitted on Tuesday night that Aguero's departure looked imminent, telling Spanish radio station Cope: "It seems as though in the coming hours we will have a final outcome to the issue that has occupied us for so long."
"It is already in its final stretch, I've asked the players to focus on Thursday's game (a Europa League tie against Stromsgodset). Unfortunately we won't be able to call on Kun (Aguero)."
Source: PA
Source: PA