The Real Madrid superstar lifted the most prestigious trophy in club football after Los Blancos won 4-1 against rivals Atletico Madrid in the Champions League Final last month.
However, Ronaldo remains coy on following up the Lisbon success with an international trophy, especially as he believes Portugal are in the toughest group.
Ronaldo wrote in an exclusive blog on sports social network Sportlobster.com: “We aren’t favourites, but we will try to perform our best as always. We know we have a difficult group stage.
“In my opinion, we have the strongest group of the World Cup, but we should take it one step at a time.
“We have an important opener against Germany, before we face Ghana and finally the United States.
“Our goal is obviously to pass the group stage and then we’ll see.”
He added: “We arrived in Brazil with hope, but we will also make sure our feet stay firmly on the ground.
“We have ambition, but with the awareness we have to set ourselves some goals step by step, game by game. We will take it calmly, but also confidently.”
Worryingly for Portugal and boss Paulo Bento, Ronaldo is currently suffering from tendinosis, as revealed by the Portuguese Football Federation.
However, the 29-year-old forward is relishing the prospect of carrying the hopes of a nation and captaining his country on the biggest stage.
Ronaldo said: “It is with enormous pride to represent and captain the Portuguese national team. It fills me with pride, satisfaction, pleasure and honour, but it is also a big responsibility.
“It is the country, which is at stake and we understand an entire nation – composed of ten million Portuguese and those living abroad – have their eyes fixed on us.
“They share the thrills with our successes and the cries with our defeats.
“I confess there are feelings, which don’t change much as the years roll. I continue to shiver, as soon as I hear the Portuguese anthem.
“I hope I win a title with the national team one day.”
Hosts Brazil, who are now ranked third in the world, kick off the World Cup on June 12 when they take on Croatia at the Maracana.
Ronaldo said Brazil is the dream destination, as he believes the Selecao’s fervent supporters will also cheer on Portugal throughout the tournament.
He added: “To compete in the World Cup in a brother country like Brazil is appealing. Portugal and Brazil have historical connections and both countries speak the same language.
“Therefore, I think it will be a fantastic experience and I believe Brazilians will also support us.”