Messi was unsuccessful in his attempt to leave Barca on a free transfer at the end of last season but is out of contract next July.
The Argentina international thrived under Guardiola during their four seasons working together at Camp Nou and they have been tipped to reunite at the Etihad Stadium.
Guardiola agreed a new two-year deal with City on Thursday, intensifying speculation of a move for Messi going through next year, but he again spoke of his belief the six-time Ballon d'Or winner should remain at Barca.
"Messi is a player for Barcelona," he said at a pre-match news conference previewing Saturday's Premier League clash with Tottenham.
"If you ask me my opinion I have a huge gratitude for what Barcelona has done for me - in the academy, as a player and as a manager, they gave me absolutely everything.
“What I want is [for Messi] to finish his career there. I would love it, I would wish it. That is what I said I don't know how many times, maybe a thousand times.
"Right now he's a Barcelona player and the transfer market will be in June or July. We have incredible games to play and achievements to try and achieve and this is only in our minds."
Guardiola's new deal will keep him at the Etihad Stadium until the end of the 2022-23 campaign and the Catalan coach is keen to add to his collection of trophies.
"All the managers are there to win titles," he said. "We did an incredible job to win eight of them.
"I say an incredible thank you for the opportunity to continue here. People say thanks to me but I say thanks to the club. They are the reason I am here.
"They gave me a lot, we continue to do the best for our people to do the best as possible."
The contract extension also ends speculation over a possible return to Barcelona for Guardiola, who was keen to praise City for the way they have handled off-the-field issues this year.
"There are many reasons why I signed," he said. "The club didn't ask the government for furlough, didn't fire one person. They showed me the club how good they are in many things.
"The decision was not just mine. The squad are all comfortable together and we will now try to continue doing what we have done in these previous seasons."