Ronaldo continued his remarkable scoring exploits against Spurs

The Portugal winger struck twice in the second half to take his goal tally for the season to 25 and seal a 3-1 victory over Tottenham at Old Trafford.

"Ronaldo was fantastic again. He took the penalty well and was able to cash in on a mistake late on for the second goal," the United manager said.

"His performances have been fantastic and his goals return is amazing."

Interview: Tottenham assistant coach Gus Poyet

Interview: Man Utd's Cristiano Ronaldo

Robbie Keane put Tottenham ahead in the first half and Jermaine Jenas missed two glorious chances either side of the break after Carlos Tevez levelled.

Ronaldo netted from the spot after Michael Dawson was sent off for deliberate handball and got his second when Spurs keeper Radek Cerny allowed the ball to squirm under his body.

It was a fantastic Cup tie where both teams contributed to what was a great game Sir Alex Ferguson

Ferguson admitted his team had not been at their fluent best but was happy enough with their contribution to an entertaining encounter.

"Overall perhaps we weren't at the top of our game all over the pitch and some players were a little quiet," he added.

"It was a very open match and I think it was a fantastic Cup tie where both teams contributed to what was a great game.

"We dominated the possession and we created a number of opportunities but maybe our final ball wasn't as good as it can be which let us down a bit.

606: DEBATE Great game to watch. We lost but am very proud Atthelane

"But the most important thing is that we're in the next round."

Spurs boss Juande Ramos reflected on what might have been after his side failed to follow up Tuesday's stunning 5-1 win over Arsenal with another Cup victory.

"We matched Manchester United at all times and had many possibilities to score," he said.

"The result is closer than the score suggests. I thought we coped well with the challenge of playing them on their own ground.

"There were some decisive moments in the game and we deserved more from it."