Barcelona goalkeeper Claudio Bravo is set for a medical at Manchester City.
The Chile international, 33, flew into Manchester on Tuesday afternoon.
City manager Guardiola said: "I cannot deny what everyone knows. The deal is not complete. After I will answer about a player who at the moment is not our player."
Joe Hart, who has not played for City this season, will start Wednesday's home Champions League qualifier second leg against Steaua Bucharest.
City have not commented on the development, but it is understood Bravo has been told he can leave Barcelona.
England international Hart, 29, began the campaign as second choice to Willy Caballero at City.
Guardiola, who took charge in the summer, has major reservations about Hart's ability to play as the kind of 'sweeper-keeper' his preferred system demands.
It was expected Hart would leave the club before the transfer window closes on 31 August, but an immediate transfer is no longer certain.
Everton, which seemed a potential destination late last week, appear to have cooled their interest - partly due to Hart's wages, which are beyond their current structure, and the early-season form of new signing Maarten Stekelenburg.
England manager Sam Allardyce has said Hart's situation is "a concern" but that he would pick the player in his squad for the World Cup qualifier against Slovakia on 4 September.
Hart trained with Cabellero at the City Football Academy on Tuesday morning.
Yaya Toure, Wilfried Bony, Samir Nasri and Eliaquim Mangala, who have also played no part for City this season, were among the 33 players who trained across two pitches.
Why Guardiola wants a 'sweeper-keeper'
Guardiola does not think Hart is good enough with his feet to fulfil the role he wants from his goalkeeper.
"From 15 years old, I grew up knowing every time we had a good build-up we created chances," former Barcelona and Bayern Munich manager Guardiola said on Tuesday.
"We can win long balls but, as fast as it goes forward, it comes back. That is why I insist with the players how important this process is.
"It starts with the goal-kick and then our build-up with three or four at the back.
"It is not a romantic issue. When we create a good build-up our forward players get the ball in a better position.
"We don't have the ball for the sake of having it. To do that is nothing. There has to be an idea.
"I would like to have the ball for 90 minutes. I know some managers prefer to play on the counter-attack. I am completely the opposite.
"Everything is fluid. When the goalkeeper, the full-backs and the centre-backs can do this, it is easier.
"The pitch is big and the space is always there. We have only had a month together. We need more time but I am pretty sure we will get it."
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