Following last week's goalless first-leg draw at the Nou Camp, Barca could have opted for a safety-first attitude for Tuesday's return meeting and then look to sneak an away goal.

However, that would be a break from tradition for a side famed for their forward play, and Rijkaard believes it would be wrong to switch to more defensive tactics for the game with United.

"I think that we have always maintained our style of play wherever we have been, with only one exception, which was when we went to play at Chelsea's ground," Rijkaard said, recalling the 1-0 defeat at Stamford Bridge in October 2006.

"There we played much more defensively than we are used to because at that point Chelsea were a very well-armed, organised and hard-working team, who were very dangerous on the counter-attack.

"But against Manchester United we have to play strong. To defend is not the correct course of action in this case. We have to play with aggression and by putting them under pressure."

Rijkaard knows it is unlikely to be easy at Old Trafford, but is adamant his side can put aside their poor domestic form and make it through to the Champions League final.

"It is a difficult ground and a strong team, but I think that we can get through," said the Dutchman, who side have won just one of their last nine league matches while on Saturday they lost 2-0 at Deportivo La Coruna - a result that ultimately ended their chances of catching Primera Liga leaders Real Madrid.

Rijkaard added: "United are a team that have no fear. They play how they know, with a good attitude, with a lot of individual talent and without complicating things.

"On Tuesday I am sure they will come out more to attack than at the Nou Camp and we must take advantage of our chances. The keys to the tie? To be aggressive and put them under a lot of pressure so as to make life difficult for them.

"To defend the result is not our style. We need to worry only about our play."

Barca may be famed for their adventurous attacking style and ability to carve open even the most watertight of defences, but that has not been the case in recent weeks with the Catalan giants having failed to score in their last three games.

It is a concern for Rijkaard, who said on television channel TV3: "We are finding it hard to score goals, but for this we need to work on our movements and have the desire to put on more effort and the desire to improve."

With the Champions League now the only chance Barca have of avoiding a second successive trophy-less season, there is even more pressure on Rijkaard heading into Tuesday's match.

Speculation has been rife this season about whether the former Ajax and AC Milan midfielder will still be in charge at the Nou Camp during the next campaign.

However, Rijkaard refused to talk about what might happen at the end of the season, saying: I live day by day and I have a lot of desire and now I want to complete the job. Then we will see.

"The club have always helped me a lot but we need to see what is best for club.

"I can imagine the logical anger of the fans (if Barca get knocked out of Europe), but we are going to give everything to bring the supporters some joy."