Schumacher has won seven F1 titles and Rossi five MotoGP crowns

Rossi's test for Ferrari at Valencia on Tuesday alongside Michael Schumacher was delayed by rain and he spun off the wet track when he drove late on.

A Yamaha spokesperson said: "He's a Yamaha rider this year and all parties are 100% aware he is testing F1 cars."

A spokesperson for Rossi's agent said: "Two wheels is his job, four wheels is his hobby."

Rossi, who has won five straight MotoGP titles, has tested with Ferrari on three previous occasions.

Tuesday's session was due to be his first on a track with other drivers.

The Italian has one season left on his Yamaha contract and Ferrari have admitted they are keen to sign him up for the 2007 season.

"We'd like to have him with us, because we believe the Ferrari-Rossi pairing is very alluring," Ferrari director Ross Brawn said.

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.

Ferrari hired Felipe Massa to replace Rubens Barrichello as their second driver for next season but his contract also expires at the end of 2006.

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.