The Spaniard addressed the media after two of his key players, Bastian Schweinsteiger and Manuel Neuer, also expressed their admiration for the Reds.
"We're up against Manchester United, one of the most important clubs in the world, regardless of their current situation," explained Guardiola. " Especially if you look back over the last 10 or 15 years under Sir Alex.
"They still have great players. It's an honour to be here again and, at the end of the day, I hope we can produce a good performance. I have a lot of respect for my colleagues and United decided to take on David Moyes. Sometimes, you need a bit more time. They believe he's a good coach and and he did a good job at Everton.
"When I see Wayne Rooney, Nemanja Vidic, Danny Welbeck, Chicharito, I know the quality of this team. And, for one or two games, they can have their performance of the season and beat us. It's the truth."
Both players were determined to spell out how dangerous United should prove to be on home turf, despite being confident on the back of a runaway success in the Bundesliga.
"My first thoughts are of Sir Alex [Ferguson] and Old Trafford and the 1999 final," Schweinsteiger replied, when asked for his memories of United. "I'm looking forward to Old Trafford. It is special here. The whole club are happy to be here, either watching or playing.
"Of course United should be one of the top four teams in England all the time. I am sure they will give everything and, if they beat the title