Schumacher (left) is on hand to give advice to Rossi at Ferrari

The five-times MotoGP champion was 12th fastest of 15 drivers on Thursday after being ninth quickest on Wednesday.

"It has been a very interesting test, as it was the first time I lapped in a Formula One car with other drivers," the Italian told the Ferrari website.

"I have to say I felt at ease and had no particular problems."

The 26-year-old Rossi spun the car several times in the early wet conditions in Valencia but improved as the track dried out.

"I did not come here to show anything to anybody but simply to broaden my understanding of a Formula One car and I thank Ferrari for continuing to give me this opportunity, added Rossi.

"In the next few months there will be more tests but now I go back to motorcycling, which is foremost in my thoughts.

"I, like Ferrari, have a task to face. We both have championships to compete in and, possibly, to win."

A Ferrari spokesman confirmed that Rossi would take part in further tests but said no schedule had been drawn up yet.

The Italian will defend his MotoGP title with Yamaha but Ferrari have said they want to sign him in 2007.

Rossi has one season left on his Yamaha contract and says he will be on the grid when the 2006 season gets under way in April.

He has tested with Ferrari on three previous occasions and could be viewed as a possible replacement for seven-time champion Michael Schumacher.

Schumacher, 37, has been the backbone of the Ferrari team for several years but his contract runs out at the end of 2006 and he has still to decide whether to continue or retire.

Britain's John Surtees is the only man to have won world championships on two wheels and four, taking the Formula One crown with Ferrari in 1964.