The 28-year-old will return to Old Trafford for the first time since leaving the Premier League club for Real Madrid in the summer of 2009.
"It will be an exciting game, and a special night for Cristiano going back to Manchester," ESPNSoccernet quotes Beckham as saying. "United has a special place in his heart. The fans love him and it will be a great occasion.
"You enjoy going back [to your former club] and I am sure it will inspire him. Many things inspire great players and him going back will be a special night.
"United did very well at the Bernabeu. It will be a great game to watch. They are two great teams with great players, so it's difficult to call."
United held Madrid to a 1-1 draw in the first leg at the Santiago Bernabeu last month.