"It's a big challenge for us, it's a test for us really, that's the way I look at it," Ferguson told reporters on Friday.
"Obviously, the development of Tottenham is an interesting one... because I can't remember, and I'm sure I'm right, ever taking United to the Lane with them challenging for the league, I don't think I've ever done that.
"So that's the change in the fortunes of Tottenham under Harry (Redknapp). And they've got some exciting players," he said at a news conference.
Fourth-placed Tottenham are eight points behind Premier League leaders United, who also have a game in hand, and Redknapp knows his team must beat them for the first time in 10 years on Sunday to keep their title challenge alive.
"I don't think they've hit the heights this year... but they keep winning games," said Redknapp. "They've not been beaten which is a fantastic achievement. Sooner or later they are going to hit top form and everybody is going to be in real trouble."
UNBEATEN RUN
Asked if United could stay unbeaten in the league this season to match the Arsenal 'Invincibles' of 2003/04, he said: "It's not impossible but I don't think they're on a completely different planet to the rest of the teams.
"They'll be favourites to win the league but I'd be surprised if they went unbeaten all season."
Tottenham last overcame United 3-1 at the end of the 2000/2001 season after Ferguson's side had already wrapped up the title.
The teams have met 23 times in all competitions since and, while Tottenham have occasionally been unlucky, the London side are still waiting for another victory over United.
"But we're playing well," Redknapp, whose side have reached the last 16 of the Champions League, told reporters on Friday. "One defeat in 13 games shows the type of form we're in as well so it's a great game to look forward to."
"We've got good players and we're a better team than the one that played Man United last year and the year before probably so we've got every chance. We're at home... we're a good team and we'll give them a real good game on Sunday."
