On the day Mourinho also officially started at Manchester United, Guardiola claimed City are in a far better position than their local rivals.
Guardiola and Mourinho frequently clashed when they were in charge of Barcelona and Real Madrid, the pair enduring a fierce rivalry that developed into full-blown animosity.
And Guardiola wasted no time in taunting Mourinho over United’s failure to make the Champions League, after City beat them to fourth spot on goal difference last season.
Although City will have to come through a qualifier to make the Champions League proper, Guardiola said they were in a far better position than United.
Guardiola was announced as City’s incoming boss on February 1, but said taking the job was never dependant on whether or not they reached the Champions League.
“I wasn’t worried,” said Guardiola. “I was coming to Manchester, I was never going to stay at home.
“But we are not in the Champions League, we have to be clear. That situation is now in this moment better than Manchester United’s, though.”
Guardiola and Mourinho will go head-to-head on July 25 in Beijing when City and United face each other on their pre-season tours of the Far East.