Surtees: stopwatch will decide Rossi move

"If he is not quick enough, then Ferrari won't chance it," he told autosport.com at the Autosport International Show. "It will be the stopwatch that makes the decision for him, that is all.

"At the end of the day, Rossi has a wonderful opportunity which I think is unique in motorsport, where a top team like Ferrari have made their circuits and cars available for someone to train. It will mean that he will have to go quicker than the others."

Surtees's comments come after Michael Schumacher said last week that the big issue with Rossi would not be whether he wanted to make the switch to F1, but whether he was actually quick enough.

"He seemed to go pretty well in the tests he has been doing with us," said Schumacher. "But then there is always the question mark, can you do the last little bit? And that's always something you have to find out yourself after more experience in the car and I'm not sure he wants to do this or not."

Surtees admitted that his switch from two wheels to four was not without difficulties - and respect for F1 cars was vital.

"You never go along and play with machinery and consider it easy," he said. "It will bite you if you do that.

"I didn't have the trouble with the speed. I could jump into a car but I wasn't particularly safe. I knew the lines for the fast corners, but when it came to the slow stuff, like Monaco, with the stop and starts, that is what I found difficult."