Carlo Ancelotti believes Real Madrid's pairing with Bayern Munich in the Champions League semi-finals represents just as much a challenge for the German champions as it does for his side.

Bayern are trying to become the first team in the Champions League era to retain the trophy and also eliminated Madrid at the same stage in 2012 on penalties after a 3-3 draw on aggregate.

"I think Bayern Munich are a great team. They have individual and collective quality and have had a great season," Ancelotti said on Friday.

"Pep Guardiola is one of the best coaches in the world and has experience. It is a very difficult tie for us, but also for Bayern Munich. I don't think it is easy to play against Real Madrid.

"At this stage of the competition when you get to the semi-finals all the teams are good. Bayern Munich could be the favourites, but our objective is to win the Champions League and if we want to win it we have to beat Bayern Munich."

Ancelotti also played down the importance of having to travel to Munich for the second leg. However, of more pressing concern for the Italian is the fitness of World Player of the Year Cristiano Ronaldo.

The Portuguese has missed Real's last two games due to injury and is expected to also be ruled out of the Copa del Rey final against Barcelona on Wednesday due to a hamstring problem.

Ancelotti confirmed Ronaldo will be sidelined for Saturday's La Liga game at home to Almeria, but is hopeful the competition's top scorer this season with 14 goals will be fit to face Bayern in the first leg at the Santiago Bernabeu on April 23.

"Cristiano is not available for tomorrow. He had a small injury against Dortmund and we thought it best to leave him out and let him have more treatment.

"We don't know if he will be fit for the game on Wednesday. I think he will recover quickly, but it is clear that if we are not going to take risks and if he is not 100 percent then he will not play in the final."

The draw does leave alive the potential for a Madrid derby in the Champions League final as Atletico Madrid were paired with Chelsea in the other semi-final.

Atletico were handed a boost just hours before the draw as UEFA released a statement stressing that goalkeeper Thibaut Courtois would be allowed to play against his parent club Chelsea despite an agreement between the clubs that would have forced Atletico a reported three million euros ($4.17 million) per match to field the Belgian international.

However, former Chelsea midfielder Tiago Mendes insisted that the 2012 European champions remain the favourites to make the final despite Atletico's heroic efforts in eliminating Barcelona in the quarter-finals.

"Chelsea are the favourites. They have a great team and a great coach," he said.

"They are used to playing finals and winning titles. It will be difficult, but we have a great desire to get to the final."