The Portuguese, who won 2014's Goal 50 on Monday, has been training with the Blancos squad in pre-season and there were suspicions he could be fit enough to face the Red Devils in the International Champions Cup clash this weekend.
However, Ancelotti has poured cold water on the notion by insisting that the 29-year-old, who has been struggling with fitness since April and did not look fully fit at the World Cup, would stay on the sidelines in the tie with Louis van Gaal's men.
"Ronaldo has been working individually, separate from the team, and he is continuing to work," he told reporters.
"We will not put him out tomorrow, as he has not trained with the full squad. He will train with the squad in Madrid, as we plan to play him in the Super Cup final.
"The plan for Cristiano was right. We programmed a good rest for him. For one month, which started on June 26. We didn't want to take any risks with him, so he will start training with the rest of the squad on August 5."
Ronaldo missed much of the end of Madrid's 2013-14 campaign, including the Copa del Rey final, but did come back in the Champions League showdown with Atletico Madrid to help them to extra-time Decima glory.
Portugal revealed that their captain had tendinitis ahead of the World Cup in Brazil and he failed to shine as his team crashed out at the group stage.