Redknapp's claim that Spurs are serious title contenders will be put to the test on Sunday when they take on the Red Devils, who top the table and have an eight-point lead over the north London side with a match in hand.
The build-up to this weekend's game at White Hart Lane has been overshadowed by former United star Beckham, who started a four-week training spell with the club on Monday.
On the mark: Redknapp is happy with Beckham's influence on his team
Ever since Beckham's arrival there has been a throng of camera crews and photographers stationed outside the club's training ground in Chigwell, Essex, hoping to catch a glimpse of the Los Angeles Galaxy midfielder.
But Redknapp rejected the suggestion that Beckham's arrival at the club had done more harm than good and maintains his squad will benefit from Beckham's presence regardless of whether a loan deal can be agreed with his parent club or not.
'David has brought a buzz around the place,' Redknapp said. 'There are lots more press here today than normal. There are people outside the ground every day.
Just peachy: Beckham departs Spurs Lodge after another day's training
'Once we come in here we train and get on with it. It doesn't affect us. It has been good having him here. Everyone respects him, likes him.
'There's nothing flashy about him, in my opinion. He just comes in and just gets on with it. He's a great role model for any footballer.'
Talks about a loan move for the 35-year-old have still to materialise into a concrete deal, with the Galaxy refusing to budge on their insistence that Beckham must return to pre-season training by the middle of February.
That would appear to have dealt a blow to Tottenham's chances of sealing a deal for Beckham, especially given that Redknapp will have to discard one member of his 25-man squad at the end of January if the midfielder is to play through February and until March.
Redknapp said he has not been informed of any progress in the talks between the clubs and hinted that any deal for the star may not be worth it unless they allow Beckham to stay until the start of March - two weeks before the Galaxy's season opener against the Seattle Sounders.
'I don't know what the situation is with permission for him to play,' Redknapp said. 'It's only two months and before you know it, a month will have gone and then it would be only a couple of weeks so it's a difficult one really.'
The Spurs boss added that the former England captain is two weeks away from full fitness and never intended to throw him into the mix for Sunday's match against his old club.
'I never felt he'd be fit enough to play this week,' Redknapp said. 'David is a fitness fanatic but getting fit to play Premier League football is very different to just going training on your own and keeping your fitness up.
Back in action: Bale has recovered from a strain and will face United
'He would be the first to admit that in his first week in training he has felt tired and it's going to be a couple of weeks before he is fit enough to play.'
It is not known whether Beckham will be in the crowd to watch Spurs take on his old team in what Redknapp admits could be a crucial match in the outcome of the title race.
'If we won I think it would open the title race open again,' Redknapp said. 'At the moment Man United are in fantastic shape. They are top of the league and really have a good lead on everybody so I think everyone at the top will be hoping that we can pull off the result, close the gap and keep everyone involved.'
Redknapp has no new injury concerns and is likely to unleash Gareth Bale down the left after he recovered from a back strain.
Tottenham lost 2-0 at Old Trafford earlier this season - partly thanks to Nani's controversial clincher - and United have not lost to their north London rivals in the last 23 meetings.
Redknapp maintains, however, that his team can beat Sir Alex Ferguson's outfit, who are likely to have Wayne Rooney and Nemanja Vidic back from injury.
'We have good players and are a better team that played them last year so we have every chance," Redknapp said.
'We are at home, we are a good team with good players and we will give them a good game.' Sir Alex Ferguson: Harry Redknapp's straightforward approach is secret to Tottenham's successChange your name to Stratford Hotspur! Tottenham MP David Lammy plans court action over switch to Olympic StadiumDavid Beckham was never going to play for Spurs against us insists Sir Alex FergusonAll the latest Tottenham news, features and opinion
Explore more:People: Wayne Rooney, Alex Ferguson, David Beckham, Nemanja Vidic, Gareth Bale, Harry Redknapp, Nani Places: London, United Kingdom