United have been in the market for a new central defender throughout the summer and are understood to have made Maguire their main target, having already missed out on the likes of Toby Alderweireld, Diego Godin, Yerry Mina and Jerome Boateng.
Maguire's performances for England at this summer's World Cup saw speculation of a move to a top-six club increase, but Puel has insisted that the 25-year-old will still be a Leicester player when the Foxes take on United on the opening day of the season tomorrow.
"I can confirm he is going to Manchester. But only for two hours when we play there on Friday. I am happy to keep Harry and all our best players. We lost Riyad [Mahrez], he was valuable for us but was important to keep all our best players," Puel told reporters.
"We have been speaking recently with the chairman and we cannot change our team just before a game just before the new season. It's not possible.
"We have to prepare this season. It was important to give Harry the feeling to come back into a squad with good strength and good ambition. He has come back with a smile. Harry is a fantastic man. He showed his quality with the national team. He came back with a good spirit and attitude."
Maguire joined Leicester last season and went on to play every minute of the 2017-18 Premier League campaign.