Juventus's record signing Cristiano Ronaldo has said his move from Real Madrid was a "well thought out decision" as the Portugal forward aims to help his new club win their first Champions League title in more than two decades.

Ronaldo, who joined the Italian champions last week on a four-year contract for 100 million euros ($117.07 million), added that he did not want to stay in his comfort zone after winning three straight European Cups with Real.

The 33-year-old left Los Blancos as their all-time top scorer with 451 goals in all competitions and won two La Liga titles and four Champions League trophies over nine years.

"I'm a person who likes to think about the present," he told a news conference on Monday. "I'm still very young and I always liked the challenges, from Sporting, to Manchester (United), to Real (Madrid) and now Juventus.

"It was a well thought-out decision. It is the best club in Italy. It has an outstanding manager (Massimiliano Allegri) and coaches so it was not a difficult decision to take."

"I am very ambitious and I like new challenges. I hope everything will go very well. Luck always helps but you have to look for it."

Ronaldo said one of the factors in joining Juve was the standing ovation given to him by the Turin club's fans on his last visit, when he scored an astonishing overhead kick for Real in the Champions League quarter-finals.

"It was a really stunning moment for me," he added. "Being welcomed this way is so rewarding. It increases your motivation to start a new adventure."

The signing of the five-times world player of the year and Champions League top scorer for the last six seasons is a major coup for Juve, who have lifted the Serie A title for the last seven seasons but have not won Europe's top prize since 1996.

"We are going to fight not only for the Champions League but for the Serie A title," said Ronaldo. "We know competition will be tough but we must stay concentrated.

"I hope I can help Juventus win it (the Champions League). They couldn't win (last year) because even when you get to the final nothing is written. I hope I can be the lucky star of this club but we will see what happens."

Ronaldo scored twice when Real beat Juventus 4-1 in the 2017 Champions League final in between triumphs over Atletico Madrid and Liverpool in Europe's elite club competition.

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