The Portugal star failed to notch his 39th goal of the season at the Nou Camp tonight but is determined to make amends on Tuesday.

Insisting he did not alter his penalty-taking technique, he said on Sky Sports 2: "I didn't change. I scored a few penalties in that side but today I didn't score - no problem.

"Now I'm going to score in Manchester."

Ronaldo insisted he should have been awarded a second penalty later in the first half when he was bundled over by Rafael Marquez.

He said: "I think he touched me. But the referee didn't give a penalty. I don't know why, I don't understand."

As for the contest itself, Ronaldo said: "It was a tough game. Barcelona played very well, they kept the ball a lot. But I think we defended well. We played well as well. 0-0 is a good result."

"They kept the ball a lot but they didn't create great chances.

"We created more chances than Barcelona."

Of the second leg, he said: "Now, we're playing at home. I think we're going to win."

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United manager Sir Alex Ferguson refused to blame Ronaldo for his side's failure to score an away goal.

The Scot revealed he thought the winger would score, but added: "He's a bit unlucky. Maybe it's come too early."

Of the second penalty incident, he said: "You're doing well to get one penalty kick. To ask for another one... I wasn't surprised."

Ferguson was pleased with his side's defending but felt they could have created more at the other end.

Describing United's performance as "professional", he said: "We sealed off the areas where teams don't normally do well against Barcelona.

"They didn't make a lot of chances. Our concentration defending the space was very good.

"We should have done better with our possession. We had opportunities to counter-attack and gave the ball away too easily."

But he added: "0-0 gives us a marvellous chance."

Ferguson singled out midfielder Paul Scholes, making his 100th Champions League appearance, for special praise.

"I thought he was one of our best players. His reading of the play outside the box was terrific. His interceptions were marvellous and he never gave the ball away."

United played without key defender Nemanja Vidic, who was ruled out by an upset stomach.

He remains a doubt for Saturday's Premier League title showdown with Chelsea.

"We think he's doubtful. We'll do our best," said Ferguson, who confirmed the Serb's condition had improved.

"Let's hope we can get him there on Saturday morning - he'll be desperate to play."