As he confirmed this World Cup will be his last, Cristiano Ronaldo took aim at pundits who have been “trying to kill me” with criticism across his international career.

Ronaldo made history by becoming the first player to score across six editions of the World Cup, with the superstar helping guide Portugal into their round-of-16 clash against Spain on Tuesday morning (WA time).

The 41-year-old used his pre-match media conference to confirm he would not be back in four years’ time, but suggested he still had fuel left in the tank.

“This will be my last World Cup, but let’s hope tomorrow isn’t my last game,” he said.

“The day will come (when I retire). But I’ll be honest. Whatever happens tomorrow, Cristiano will leave with a clear conscience, not 100%, but 1000%. Because I’ve given everything in football.

“I don’t need it, I have a good life, but it’s about passion. I play football because I love it... You have to enjoy every day. And I’ve scored three goals (at this World Cup).

“I’m not doing too badly, right?”

Ronaldo said he had thrived in the face of criticism and doubt from some quarters to carve out one of the most decorated careers of the modern era.

“You have been trying to kill me for the past 23 years, but you must have seen that is not worth it, it’s a waste of time, but you try and try and try and try and try,” he said.

“As I said before, (I will stop) when I choose, not when you choose, you always ask the same question.

“I don’t want to draw attention to this because it is less important.”

Portugal enter their clash with Spain in Dallas as $2.76 underdogs to advance, with the Spaniards considered by bookmakers as the third most likely team to win the tournament behind France and Argentina.