Dimitri Seluk accused the City manager of “humiliating” Toure, 33, by leaving him out of the club’s Champions League squad at the start of this month.
The Ivorian midfielder, who announced his retirement from international duty on Tuesday, has not figured in a single City match-day squad since then.
Guardiola stated in a press conference:
“The day after that, his agent spoke and in that moment, Yaya is out,”
“Unless Mr Dimitri Seluk comes back to the press or to his friends in the media because he hasn’t the courage to call me, he goes to the media and apologises to Manchester City first of all, then his team-mates and afterwards the trainer.
“When that happens, Yaya will be part of the group and he will have the chance to play.”
While Guardiola said that Seluk should say sorry for his comments, the club later indicated the manager wanted an apology from Toure.
Toure has recovered from a migraine that made him unavailable for Saturday’s 4-0 Premier League win over Bournemouth, but he will not be considered for Wednesday’s League Cup tie at Swansea City.
Seluk had said:
“If he (Guardiola) wins the Champions League for City this season, then I will travel to England and I will say on television that Pep Guardiola is the best manager in the world.
“But if City don’t win the Champions League, then I hope that Pep has got the balls to say that he was wrong to humiliate a great player like Yaya.”
Toure, who is in the final year of his contract at the Etihad Stadium, has featured just once for City since Guardiola’s arrival.
He played the full 90 minutes of their Champions League play-off second-leg victory over Steaua Bucharest in August.
“I cannot accept as a coach that every agent, when his player doesn’t play, goes to the media and speaks.
“I know how much Dimitri Seluk loves Yaya Toure. If he loves him, show me by apologising to Manchester City for what he said in the papers.”
Guardiola said that, as a player at Barcelona in the early 1990s, he would never have dared to allow his agent to speak out against Dutch legend Johan Cruyff, then the club’s manager.
“I cannot imagine in my day when a player’s agent would go to the media and speak against Johan Cruyff,
“Maybe it’s the new era, but I’m from the old generation, and an old-generation agent has to make his players his job and the coach his job.
“Today agents believe they are more than they are. If you have a problem, we can talk. Until he speaks, Yaya isn’t going to play.”
Guardiola said the decision to omit Toure from his Champions League squad had not been an easy one.
“It was so difficult for me to leave him out of the Champions League squad. So difficult,” he said.
“I know him and I know he’s a good guy. It was difficult as well for Aleix Garcia.”
Toure has been at City since 2010 and has won two Premier League titles, two League Cups and one FA Cup during that time.
While he will play no part at Swansea, captain Vincent Kompany could return, having not played since April after undergoing groin and thigh surgery.