Portugal forward Helder Postiga has insisted that teammate Cristiano Ronaldo can shake off his injury problems to lead the side for the rest of their World Cup campaign.

Ahead of their crucial Group G clash with the USA on Sunday night, Postiga is confident about Ronaldo's fitness, despite reports suggesting that the captain was in danger of being ruled out of the tournament with a knee injury.

"If he is available enough to train with us that's probably because he is feeling well," the Valencia striker told reporters.

"He's been training with us all these days and as usual he always gives his best. He's just fine."

Portugal are searching for their first point in Brazil after being thrashed by Germany in their opening game.