However, the 45-year-old refused to divulge any more details about his City switch, with the Bundesliga leaders set to visit fourth-place Bayer Leverkusen on Saturday.
"People know what I said. I already said a few weeks ago what happened. If they don't believe me, I can't do anything about it," said an irritated Guardiola.
He did concede that "initial talks were held in May or June" regarding a move to City, but vowed not to say anymore about his future employers.
"I know it's new at Bayern where a coach has never left of his own accord," the Spaniard added. "I will stay focused on my team until the final day to give the best of myself."
Guardiola announced in December that he would leave Bayern Munich in May after three years at the helm, with the intention of coaching in England next season.
His Bayern side are on course for a record fourth straight Bundesliga crown with an eight-point gap separating themselves and nearest challengers Borussia Dortmund.
The Bavarian giants are also through to the last 16 of the Champions League and will face last year's finalists Juventus in Turin later this month in the first leg.
Pellegrini has dismissed suggestions that Guardiola was manoeuvred into the club behind his back.
Pellegrini, whose side are set for a crucial showdown with Premier League leaders Leicester City on Saturday, said he was not kept in the dark as the Bayern Munich boss was ushered into the City hotseat.
Guardiola, who won back-to-back German league titles with Bayern and is on course for a third after joining in 2013, agreed a three-year contract with City this week and will begin work ahead of next season.
"It's important for everyone to know that I knew what was happening and that no one was doing anything behind my back," Pellegrini told reporters on Friday.
"It's important to talk about this season and not the next one."
Pep Guardiola timeline
- Telegraph