Cristiano Ronaldo said he did not want to use his injury problems as an excuse after Portugal's hopes of progress at the World Cup were all but ended by Sunday's 2-2 draw with the U.S.

Ronaldo has been suffering with a tendinosis issue in his left knee for months, a problem which greatly hampered his contribution to the end of Real Madrid's club season, and which some reports have claimed could now cause him even more serious problems in future.

The Portugal captain was below his best in the Group G clash in Manaus, never troubling U.S. goalkeeper Tim Howard throughout the 90 minutes, but still providing the cross from which substitute Silvestre Varela headed a stoppage-time equaliser.

Speaking to AS after the game the 29-year-old admitted his knee was a problem, but said he did not want to use the injury as an excuse for his performance.

"I do not want to use my physical problems as an excuse," Ronaldo said. "That is already overcome. I am here to show my face, to try and give my best, to run... It is not worth talking more about what I have. There is news in the papers every day about what I have, the knee, the tendonitis, about that, the other...

"But I do not want to justify myself. I am here in body and soul to help the national team and we have not achieved our objective. Now we will see what happens in the next game."

Ahead of the final set of games Portugal have just a very small chance of progression from the group, needing to heavily defeat Ghana in Brasilia on Thursday while hoping the U.S. can beat Germany in their game being played at the same time. However the U.S. and Germany know that a draw in their meeting in Recife will send them both through to the round of 16.

Ronaldo also said that pre-tournament expectations that Portugal could actually win the tournament had been shown to have been unrealistic.

"All the teams are here to win and we were never favourites," he said. "It was just a make-believe dream that Portugal could be world champion, because everything is possible in football, but other countries have better teams. Maybe they deserve it more than me."

This summer's showing has been a further disappointment at the World Cup for the former Manchester United player, who has now scored just two goals in three finals -- a penalty against Iran in the 2006 competition, and a strike in the easy 7-0 group win over North Korea in 2010.