Bale has been in the form of his life this term, scoring 16 Premier League goals to lead Tottenham's top-four charge and challenge for Europa League honours.
Meanwhile, rumours continue to persist that Rooney, who failed to start his side's Champions League last-16 second-leg defeat to Real Madrid on Tuesday, is set to exit Old Trafford this summer.
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"They are two top players. You always want to play with the best, but I think it would be very difficult for them to join Barca. They are already at great clubs," the 25-year-old said at the launch of 'Team Messi'.
The Argentine went on to express his belief that Barca can overturn a two-goal deficit at the Camp Nou against Milan in order to progress to the last eight of the Champions League.
"We can do it. It will be complicated, but we'll get our chances to go through," he added.
"Never did the Italians play in our box. We will do everything to try to beat them like they did to us. Italian teams are very well organised and leave no spaces at the back.
"Hopefully Tuesday is the day that we can score the first goal from open play.
"Bayern [Munich] and [Borussia] Dortmund are almost certain to be in the last four, they are doing great and they deserve to be [in the knock-out stages]."Madrid are proving to be very strong and are a candidate to win the Champions League, as were [Manchester] United."
A wretched run of form has seen the Catalns defeated in three of their last five matches, and Messi is determined to bounce back from the jaws of adversity as quickly as possible.
"I've had bad spells before. I've experienced many losses in my time, but I hope to enjoy many more successes like we've had in recent years," he added.
"I'm not sad. Hurt, yes, but not sad. We don't like to lose, but this is the perfect time to bounce back. I have the desire to win every day and I always want more."
Messi also spoke about Argentina's ambitions at World Cup 2014 in Brazil and revealed that winning the international trophy would be the "pinnacle" achievement of his footballing career.
"The national team is going through a good spell, having overcome some complex situations, and we have a lot of room for improvement. We come alive in big games, and we want to book our place in Brazil for the World Cup," he remarked.
"Winning [the World Cup] would be the dream of any footballer. It would be the pinnacle, but we can only talk about that for now."