MONACO, May 25 - Ferrari were serious about bringing Valentino Rossi to Formula One and the MotoGP champion may not have closed the door completely on a future switch, according to technical director Ross Brawn.

"We were very impressed with what he was able to do," the Briton told reporters at the showcase Monaco Grand Prix on Thursday, a day after the charismatic Italian announced he was staying in motorcycling.

"Both sides had to decide if we wanted to go forward with it and I think he felt he had his hands full with his motorcycle career," added Brawn.

"I think the difficulty he is having this year focused him more on that."

Rossi has dominated motorcycling's top category for the past five seasons but is struggling with his Yamaha this year and languishes in eighth place after five races as a new wave of Honda riders comes to the fore.

"I think after several championships he was looking for perhaps a new challenge and he's found a new challenge in his motorcycle career this year because its not going as well as he would hope," said Brawn.

Ferrari have given Rossi several tests over the past year amid speculation that he could take over from seven times champion Michael Schumacher.

"It would have been very exciting," said Brawn.

"It's difficult to predict what the final results would have been but he was very impressive with all the running we did, impressive enough that we would have considered him seriously if we had the capacity to offer him to drive for us and if he wanted to do it."

Asked whether the 27-year-old Italian might still be able to break into Formula One in a couple of years, Brawn recognised it would be increasingly unlikely but not impossible.

"Of course the longer you leave it makes it a little bit more difficult," he said. "But I guess he could in a couple of years reconsider."

The technical director said also that Rossi had no inside information about Ferrari's plans for 2007 and that had not been a factor in his decision.

Ferrari are still waiting for 37-year-old Schumacher to decide whether he wants to continue and have also been strongly linked to McLaren's Kimi Raikkonen. They also have Brazilian Felipe Massa on their books.