Michael Schumacher insisted last night he would compete in the United States Grand Prix on Sunday week having been warned he could risk being stripped of his world title.

The German had been given the option by his Ferrari team of not competing at Indianapolis amid the uncertainty following last week's terrorist attacks.

But Schumacher, who wrapped up his fourth world title in Hungary last month, was told by Formula One supremo Bernie Ecclestone that playing safe and staying at home could put his drivers' crown at risk.

Schumacher headed off any thoughts of him losing the championship in such controversial circumstances by confirming that if the race did go ahead - and it surely still has to be in doubt - then he would be there.

"I've heard about these rumours but I am not thinking at all about not driving there at the moment," said Schumacher.

Ecclestone had upped the ante in the debate raging in Formula One about next week's race by saying before yesterday's Italian Grand Prix that Schumacher could be docked points and lose the title.

"Let's get one thing straight, Michael Schumacher is not yet the 2001 world champion,"

Ecclestone has been quoted as saying. "Anything could happen. Maybe he could lose his points over one of the next three races. I'm sure that won't be the case, but it could be." It would seem unlikely that even Ecclestone would move to strip Schumacher of the title given his domination of the championship this season or whether it was in the rules anyway.

The 32-year-old has won eight of the 15 races and with just the US and Japan left is a massive 50 points ahead of second-placed Scotsman David Coulthard.

The final decision on the US Grand Prix is likely to be made in the next couple of days. The teams need to be told quickly to give them enough time to get their cars and other equipment ready by Friday to be cargoed out to Indianapolis.

Meanwhile, Alex Zanardi's condition was described as more stable but still critical after a second operation yesterday, two days after the Italian lost both legs in a horrific high-speed crash at a CART race in Germany.

Dr Walter Schaffartzik from the hospital where the former Formula One driver was being treated said the latest operation, to remove bone splinters and reduce the risk of any infection, had been performed successfully yesterday afternoon.

"We are satisfied with the way his wounds are healing," Schaffartzik said. "His condition remains critical but it is no longer as acutely life-threatening. It has become more stable but we have to remain cautious because complications can still occur at any time."

The 34-year-old Italian had to have both legs amputated in an operation which lasted over three hours on Saturday night, a few hours after his accident on the official European debut of the US racing series.

Zanardi also suffered several pelvis fractures which did not require surgery but what worried doctors the most was that he had lost a lot of blood.

"Medically speaking he is not in a coma but he receives medicine to fight pain, which keeps him asleep," Schaffartzik said.

Zanardi, who survived a serious Formula One crash in 1993, had just come out of the pits after 142 laps of the 154-lap race at the Lausitzring oval when his Honda/Reynard was struck hard and destroyed by the Canadian Alex Tagliani's Ford-Cosworth/Reynard.

Tagliani's condition was far less serious. The Canadian sustained only light injuries and was discharged from hospital on Sunday afternoon.