Andrei Arshavin, who scored four goals last week against Liverpool, is cup-tied, having played earlier in the competition for Zenit St. Petersburg, and Dutchman Robin van Persie, who had a goal and assist in Arsenal's 3-0 win over Villarreal two weeks ago, is injured.
"We will go there with belief," Wenger said of the trip to Old Trafford. "We will go there like we do everywhere in Europe to try to score and win."
Arsenal's attack has been on fire in recent weeks, scoring 14 goals in five games.
United, which scored five goals in 22 minutes on Saturday against Tottenham, should be close to full strength. It will be only missing captain Gary Neville.
The game will mark the 800th appearance for Ryan Giggs with Manchester United.
"They don't come much bigger than a Champions League semifinal at Old Trafford," the Professional Footballers' Association Player of the Year said, "and I am looking forward to it, but I am more interested in beating Arsenal rather than the 800th appearance."
Manchester United:1-van der Sar; 22-O'Shea, 5-Ferdinand, 15-Vidic, 3-Evra; 8-Anderson, 16-Carrick, 11-Giggs; 7-Cristiano Ronaldo, 9-Berbatov, 10-Rooney.
Arsenal: l-Almunia; 27-Eboue, 5-Toure, 20-Djourou, 40-Gibbs; 14-Walcott, 17-Song, 8-Nasri, 4-Fabregas; 25-Adebayor, 26-Bendtner.
Referee:Claus Bo Larsen (Denmark).