But the City boss, when asked by reporters on Friday to compare Mbappe with Lionel Messi, whom Guardiola managed at Barcelona, reacted cautiously.
"Nobody can sit at the same table as Messi. Maybe Mbappe, he's a top player, he will be an outstanding player, I'm pretty sure of that.
"But to equal what Messi has done in 10 or 12 years, or Cristiano (Ronaldo), for example, we have to wait. I appreciate Mbappe wouldn't like me to put more pressure on his shoulders."
Guardiola said Argentine forward Messi had produced his best season after season.
"I think Messi has the numbers of 60-70 games every season, in the big games, always being there to score and assist, never injured, always plays every three days, never injured because he controls his body," he said.
"That's why I don't think we help with hypothetical suitors for him, saying you are going to be the new guy. So let Mbappe have the fantastic career he will have and after we"ll see in the future."
Guardiola also said he had warned his Manchester City stars about the perils of social media although he has no intention of curbing their use of it.
A number of City players, in particular new French international full-back Benjamin Mendy, are prolific users of social media.
Former Monaco defender Mendy was widely criticised when he mocked Brighton's Lewis Dunk on Twitter after he scored an own goal in the match against City on the opening day of the season.
Guardiola, 46, admits that it is an area that he does not understand but, while he is happy for his players to continue to use it, he has issued a message of caution.
"No," said Guardiola when asked if he intended to limit players' use of social media. "They can communicate, it's part of their lives now.
"Today is a different world than what I lived in. Maybe in my period if we had Twitter I'd use Twitter.
"I just want respect for the other ones. I don't want to see disrespect for team-mates, the opposition, the club, for the fans, for the issues happening in the world. That I don't want to see from my players, and we spoke about that.
"Of course, everybody is free, I'm not a guy to say 'ban that, ban that'. They are adults, some of them are fathers, but respect, be careful what you write, be careful what you say because I don't want other guys to feel uncomfortable with what they say on Twitter."