"The offer from Manchester United is fantastic," Hargreaves told German daily Bild on Wednesday.
"Particularly as an England international, it is of interest and you never know if such an opportunity will arise again. Now is the time to take the next step to develop even further."
United are looking to strengthen their midfield after former skipper Roy Keane joined Scottish giants Celtic, before announcing his retirement from professional football.
The Premiership side signed Tottenham midfielder Michael Carrick and they set their sights on landing Hargreaves although he has just signed a contract extension with the Bavarian giants.
However, Bayern do not have any plans of selling the 25-year-old midfielder.
"I have just spoken with [general manager] Uli Hoeness and he is absolutely clear that selling Owen Hargreaves is not an issue," Bayern press officer Markus Horwick was quoted as saying by Sky Sports Network.
"I think what Mr Hoeness says is enough to end any speculation. Owen Hargreaves will be staying with us for the remaining four years on his contract."
Hargreaves was part of England's squad in the World Cup, where they were eliminated at the hands of Portugal in the quarter-finals.