Real Madrid forward Cristiano Ronaldo has vowed to "keep going at the highest level for years to come", as he offers a strong response to his critics.

The Portugal international, the winner of a fifth Ballon d'Or at the end of last year, has been far from his best domestically speaking this term.

Ronaldo has netted eight times in 17 La Liga starts, dropping below his impressive goal-a-game figures of the past, leading to rumours that he may even be allowed to leave the Bernabeu in the summer.

Speaking to Italy's GQ magazine, however, the 33-year-old insisted that it is far too early to consider winding down his career elsewhere.

"On a personal level, this is a fantastic time for me," he said. "I have a growing family and I am very happy with my life. On a professional level, I have had two very good years in which I have won titles with my club and with my national team. I feel that I can keep going at the highest level for years to come.

"Life is a challenge from all perspectives and I try to be at my peak, physically, because this is very important in my profession. I have to be at 100% and I take this very seriously.

"To maintain this level, you need to make sacrifices. There are certain things that I could do when I was 20 that I can't do today. You have to try and find a balance. It's the finer details that make a difference.

"I am ambitious, very ambitious. People should chase their dreams. I chased mine and I want to keep doing so, to improve and achieve even more goals. I believe I've had some memorable performances throughout my career but can't recall any in particular. I try to focus myself more on the present than on the past."

Paris Saint-Germain youngster Kylian Mbappe, who Ronaldo will come up against in the Champions League next week, has backed the Portuguese superstar to recapture his peak form.