Guardiola: Yaya Toure must apologise to Man City for agent comments before selection again
The 33 year old has made one appearance for City this season and was left out of their Champions League squad.
His agent, Dimitri Seluk, said the midfielder had been "humiliated" and Guardiola should apologise to him if City do not win the competition.
Guardiola said: "He must apologise. If he doesn't, he won't play."
The Spaniard also wants an apology from Seluk.
He said it had been a difficult decision to leave Toure out of his European squad.
"If he has a problem, he should speak to people at the club," said Guardiola.
He added Toure, who returned to training on Monday after a migraine, had not had the "courage" to call him.