City finished two points above Arsenal to win their fourth consecutive Premier League title last season, having also beaten the Gunners to the 2022-23 crown.
Guardiola said he was again “concerned” about Mikel Arteta’s side ending City’s reign after watching Arsenal beat German champions Bayer Leverkusen 4-1 in a pre-season friendly.
“I have been concerned for many years with how good they are because every year they are getting better,” Guardiola said.
“I see Arsenal playing at the same level as last season. They are on fire. Every year it looks like they are more and more difficult.”
Guardiola was also asked about the possibility of replacing Gareth Southgate as England boss.
The 53-year-old has been linked to the post since Southgate stood down. His City contract expires in 2025 and he has stated his desire to manage an international team.
“I have to decide what I want to do in my life,” said Guardiola.
“If I want to continue here, take a break, train national teams or not. Right now I am here and as you arrive at the competitions my energy rises again, so I am fully excited for the season because I see things that I like here.”