The 25-year-old will be in Leicester's squad for Friday's Premier League opener at Old Trafford and Puel said joking: "I can confirm he is going to Manchester but only for a couple of hours.
"I am happy to keep Harry. He is our best player. I am a football manager and I want to keep our best players for the squad and for our season.
"Harry is happy to remain with us. And I am happy with his attitude. He came back with (Leicester and England team mate) Jamie (Vardy) with a smile, with freshness."
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Leicester have already lost influential winger Riyad Mahrez to Manchester City in the current transfer window, and Puel wants to keep the rest of his core group of players at the club.
"For us it (a Maguire transfer) is not possible. It is not serious. We have to prepare for this season with good possibilities," he added.
"We want to keep good ambition. We lost Riyad Mahrez, who was a very valuable player for us, so it was important to keep our best players and have good additions to the squad."
Earlier on Thursday, young Croatian defender Filip Benkovic became the sixth new arrival at the King Power Stadium after Jonny Evans, Ricardo Pereira, James Maddison, Rachid Ghezzal and Danny Ward.
(Reporting by Hardik Vyas in Bengaluru; Editing by Ken Ferris)
