Hargreaves is expected to complete his move to United by the end of the week.
He told Sky Sports News: “Owen is a great player. We are looking for big players and players to take us to the next level.
“There’s going to be competition for places. Paul Scholes is one of the best midfielders in the world and Michael Carrick’s had a good season.
“He (Hargreaves) realises that coming to Manchester United and he’ll be up for the challenge.”