The Austrian - champion in 1975, 1977 and 1984 - said at the American Grand Prix that he would have become "bored" if he was winning as many races as Schumacher.

"Winning all the time, I would have started to do something else with my life," he said.

Lauda walked away from F1 in the middle of the Canadian Grand Prix weekend in 1979 to concentrate on running an airline. He returned in 1982.

But the Austrian, now the boss of the Jaguar F1 team, paid tribute to Schumacher's talents as the greatest driver he has seen in F1.

"He's really the best, as long as I can think of racing, by producing results and his consistency in always being better every year, he is by far the best from my point of view.

"Because nobody else could do this so far."

Earlier, Schumacher rejected claims that Ferrari's domination of F1 is ruining the sport.

Attendance at this weekend's US Grand Prix at Indianapolis is expected to fall well short of the 175,000 who watched last year's race.

Race organisers have blamed the recession and Schumacher's serene march to the drivers' title for the comparative lack of interest.

But Schumacher insists Ferrari's grip on the sport is not as tight as it seems, even though the Italian team have won 13 out of 15 races this season.

"An easy double victory. And all those who think that our supposed dominance is damaging the sport felt their opinion validated.

"I also felt validated, in my opinion that we would have had to fight very hard for this dream result if our competition at BMW-Williams hadn't run into problems so early.

"If the engine in Ralf [Schumacher's] car hadn't exploded and Juan Pablo Montoya had not had other problems then the Italian Grand Prix certainly would not have turned into such a dream race for us."

Schumacher, however, was forced to concede that Ferrari have a great chance of winning the final two races of the season in the USA and Japan.

That would see them equal McLaren's record of 15 wins, though Ferrari's rivals achieved the feat in a 16-race campaign.

"We have such a good car that of course it would be great if the last two races went in our favour," added Schumacher.

"I am not going to make predictions about Sunday's Grand Prix because a lot will depend on tyre performance.

"We know our car is close to perfection on all types of track and we will definitely be competitive, even though I cannot say to what degree."