LONDON -- Michelin has challenged Formula One's governing body to disqualify half the grid at the next Italian Grand Prix after the FIA raised doubts about their tyres.

"If the FIA want to disqualify 10 cars from the final results, then go ahead," Pascal Vasselon, Michelin's Formula One programme manager, told Italy's Gazzetta dello Sport newspaper on Tuesday.

He said that the French company's tires were legal and Michelin saw no reason for change at a decisive stage in the championship.

Ferrari's Michael Schumacher, whose car uses Bridgestone tires, is clinging to the overall lead by one point from Williams' Colombian Juan Pablo Montoya and two points from McLaren's Kimi Raikkonen.

Williams, who lead Ferrari in the constructors' standings by eight points with three races remaining, and McLaren both run on Michelin tires as do Renault, Jaguar and Toyota.

Vasselon said that the tires to be used by Michelin teams at Monza next week and in testing at the circuit starting on Tuesday would have the same dimensions as those used at the last Hungarian Grand Prix.

"Since our tires have been considered legal up to now there is no reason to change them and above all we question the change in the interpretation of the rules with the championship still under way," he said.

"The tires for these Monza tests were manufactured in the days immediately after the Hungarian Grand Prix and there was clearly not time to change them."

The International Automobile Federation (FIA) warned teams last week that stewards would be looking closely at tires after the race as well as before to ensure they conformed to the maximum amount of tread allowed in contact with the road.

FIA sources said information received after Hungary, where Michelin cars filled the top seven places, suggested that Michelin's front tires could be in breach of the regulations under some circumstances.

Baumgartner replaces Firman at test
Hungarian Zsolt Baumgartner will replace injured British rookie Ralph Firman at the Monza Formula One tests this week, his Jordan team said on Tuesday.

Baumgartner became the first Hungarian to start a Formula One race when he replaced Firman at the Hungarian Grand Prix on August 24.

He will join Italian Giancarlo Fisichella at Monza on Wednesday for a two-day session. The circuit near Milan hosts the next round of the championship, the Italian Grand Prix, on September 14.

Baumgartner will also drive Jordan's third car in private testing at Monza on the Friday before the race.

Firman injured his left heel and suffered concussion after crashing at high speed in Saturday free practice before the Hungarian Grand Prix when the rear wing of his Jordan flew off as he accelerated down the straight.

Jordan said on Monday that the 28-year-old, who had a medical in London, had decided to miss the Monza tests to allow himself more time to recover.

Schumacher appointed ambassador of San Marino
ROME -- Reigning Formula One champion Michael Schumacher has been appointed an ambassador of San Marino, a statement on Ferrari's official Web site announced on Tuesday.

The 34-year-old German driver, who has won five world titles, was offered the role by the republic on the Italian peninsula on the basis of his previous humanitarian work for Unesco and charity.

"I feel honored and proud to have been nominated as an ambassador of the Republic of San Marino," the 34-year-old told reporters at a ceremony on Monday.

"This appointment is a further impetus for the work I already do," he continued.

"Unfortunately, it is a fact that many people need our help. In particular, our attention, compassion and support is needed to help children who are not able to help themselves."

Having dominated last season's Grand Prix competition with 11 wins out of 17 races, Schumacher is struggling to retain his grip on the title.

With three of this season's races remaining, the German has a one-point lead over his nearest rival, Juan Pablo Montoya.

His standing in the tiny republic, however, remains unchanged, having won the San Marino Grand Prix at Imola earlier this year shortly after his mother died.