The Spanish manager points to Sir Alex Ferguson's side's strength in depth after their second string comfortably defeated Schalke in the second leg of their semi-final
Goals from Javier Hernandez and Nemanja Vidic gave United a 2-1 win over Carlo Ancelotti's team, meaning that the Red Devils need take only one point from their final two Premier League matches - against Blackburn Rovers and Blackpool respectively - to overhaul Liverpool's championship record and ensure a 12th title in 19 seasons.
And Barcelona boss Guardiola, whose own side are only one point away from the title in Spain and who meet United in the Champions League final at Wembley on May 28, has hailed the strength of his team's final opponents.
"They have a great squad," said Guardiola.
"A great team, extraordinary players."
Guardiola, who will be aiming to beat United for the second time in three years in the final after succeeding in 2009, added: "They played a Champions League semi-final with a team full of reserves and they won 4-1 - that says everything you need to know about the quality they have."