"They will strike back, that's what they want. They are Portuguese and proud and will give a fight. They want to strike back.
"If anybody here thinks they come here and give the game up, leave their star players at home or whatever they are mistaken. It's Champions League and the whole world is watching. What do you think?"
Liverpool face United at Old Trafford in the Premier League four days later in a battle for second behind runaway leaders Manchester City.
"I don't think for a second about resting anybody. I know it's Manchester United afterwards but we cannot change it," he added.
Liverpool recorded a convincing 2-0 victory of Newcastle United on Saturday, extending their unbeaten run in the competition to five matches and moving up to second.
"Mentality is always the part of the personality where you can improve most, all of us," Klopp said.
"You cannot win any race in the world without being aggressive. That's how it is. So in the situation we are in now, it's clear we will not win the Premier League but it’s very positive."
(Reporting by Hardik Vyas in Bengaluru; Editing by Peter Rutherford)
