The Manchester City boss believes Ole Gunnar Solskjaer’s side will try to use their pace to exploit his side on the counter-attack, as they did so effectively in last month’s 2-1 defeat in the Premier League.
A series of lightening quick breaks left City exposed during the first half at the Etihad Stadium and Guardiola appreciates the threat United pose.
He believes United’s pace can be a problem for any team in the world, but says his side must ensure they get a positive result ahead of the second leg at home.
“It will be quite similar,” he explained after the 4-1 FA Cup win over Port Vale. "Of course, at Old Trafford it is different than the Etihad.
"It is a team that is built to run. When they can run, they are one of the best teams, not just in England, because of the pace they have with James, with Greenwood, Martial, Rashford and Lingard.
“They are good. I saw the lineup against Wolves and they made a lot of changes so I guess they will be focused.
“There are two games. We have to go there and try to take a good result for the second leg here with our fans to try and reach the final of this competition for the third year in a row.”
Despite suffering at the hands of United’s counter-attack, Guardiola says he will not be altering his game plan for the trip across the city.
He admits his players need to improve in certain areas, but he was not too disheartened by the display in the previous encounter.
In particular, the 48-year-old was pleased with the number of chances City created at the Etihad and his side will go to Old Trafford with the intention of scoring goals rather than trying to contain the hosts.
“We have to reduce the mistakes in the build-up and be prepared for that,” Guardiola added. “But we have to do our game.
“I’m not going to prepare to stop them running. We have to go there to score a goal, to play our game and try and take a good result back here.
“I would like to play at Old Trafford like most of the parts [of the league game], except the first minutes when we conceded three or four chances when they could run.
“The rest of the game I liked the way we played. We created a many chances. I would like to play similar.
“We don’t have much time, but we have two and a half days to train and prepare the game we want to do.”