The event, which drew more than 200,000 fans on race day last year, will be America's biggest sporting showpiece since the September 11 attacks on New York and Washington.

Organizers have promised heightened security for the penultimate race of a championship already won by Ferrari's Michael Schumacher.

Some measures, such as inspection of all coolers, backpacks and handbags at the circuit gates and a greater police presence, have been announced.

With no track action on Thursday and the giant public grandstands silent in the afternoon sunshine, the police presence was low-key.

Former world champions Mika Hakkinen and Jaques Villeneuve, joined by Juan Pablo Montoya, Kimi Raikkonen and Pedro de la Rosa at a news conference, expressed no concerns.

They smiled and shook their heads when asked if any of them had safety fears.

The last race at Monza in Italy was run just days after the attack. Some suggested the race should have been cancelled as a mark of respect to the thousands killed in New York.

Going racing
Canadian Villeneuve, 1997 champion for Williams and now at British American Racing, said the situation had changed.

"Once you got in the race at Monza then nothing else existed for this hour and a half of racing and that's how it should be in anything you do," he said.

"There's been more time since Monza and everything is a bit different...the shock is still there but you just have to go along and there's no reason for us to do anything different here."

Hakkinen made it clear that his mind was focused on racing in what could be the penultimate grand prix of his career if he does not come back from a year's sabbatical next season.

"I have a commitment to the team to finish the season and I'm going to go for it in these two races," said the two times champion.

Montoya, who won the Indy 500 on Indianapolis' famous oval circuit last season while the reigning CART champion, is returning for his first U.S. Grand Prix, after winning at Monza.

The Colombian Williams driver said that first win was a big relief and a reward for his patience.

"We don't know how competitive we will be here," said Montoya, who has been on pole for three of the past four races. "We will see how we adapt to this very particular circuit.