Portugal's goalkeeper, Beto, is insisting Cristiano Ronaldo will be fit to play the United States on Sunday.

Ronaldo has been dealing with a knee issue for weeks and there had been reports that Portugal's doctor advised him that his career was at risk by continuing to play.

"Ronaldo didn't leave training early," said Beto. "He finished his training at the same time as the rest of the players," Beto said at a press conference. 

"Cristiano is 100 percent fit to play. Every match he starts to play, it's because he's fit to play.

"He loves football but his body is the most important thing for him, to be fit, to be healthy so if he starts the match it's because he's ready, he's fit."