Two teams knowing that they must improve on their opening performance at the World Cup finals meet in Frankfurt.

Portugal edged a 1-0 win over Angola, but Iran's 3-1 defeat by Mexico left their hopes of progressing to the knockout stages hanging by a thread.

The European side's preparations have been disrupted by doubts over the fitness of Manchester United ace Cristiano Ronaldo.

The winger is reported to be struggling with a hamstring injury, although team officials insisted Ronaldo missed training in the week due to tiredness.

Better news came with Barcelona midfielder Deco returning to full training after recovering from the foot injury that prevented him playing in the 1-0 win against Angola.

Midfielder Costinha has warned his team-mates to be aware of the threat posed by Iran, saying: "It will be a difficult game. They lost the first game, so in this game they will play even harder because, if they lose, it will be difficult for them to qualify."

Iran coach Branko Ivankovic is well aware that his side face an early exit if they lose again, but he is likely to be without the services of veteran striker Ali Daei, who is struggling with a back problem.

"Ali Daei has missed training because of a back injury. I think it is very hard for him to play against Portugal," Ivankovic confirmed.

However, there is better news about key midfielder Ali Karimi, with Ivankovic adding: "Karimi's injury is an old one and he has had problems with it, but I think he will be okay for Portugal."

Fellow midfielder Ferydoon Zandi, born in Germany, is another major doubt as he struggles with both an injury and a slight fever.