The two-time champion clocked the fastest time of the day in one minute 13.387 seconds, 0.165 ahead of his old Ferrari rival Michael Schumacher.

Because of a system problem, the Finn had earlier managed only four laps on a cold and overcast day in Indiana.

But a lightning engine change by his McLaren mechanics put him back in the fast lane for the afternoon session.

"Today was a great day. We did a very good job with the car," said Hakkinen, who is taking next year off and is racing at Indianapolis after speculation that he might not attend.

"The mechanics changed the engine in 35 minutes and that is a very great job," he said.

"I want to win, I feel good, confident and a happy person. I am getting on with everyone in the team and I feel happy in the car."

Hakkinen said he had been waiting a long time to tell the world about his decision to take a sabbatical and now he had done so he could enjoy his racing.

"It has been difficult ... and I feel relaxed now and not worried about anything any more," he said.

Schumacher, who wrapped up the championship in August, had shown he was back in business after a difficult two weeks with the fastest time in the opening session.

The German was a pale shadow of his usual self at the last race in Italy in the wake of the suicide attacks on America.

Brazilian teammate Rubens Barrichello, fighting McLaren's David Coulthard for second place in the standings, was third fastest in 1:13.584 ahead of the Scot in 1:13.656.

Both sessions were quiet, with several cars involved in harmless spins.

Colombian Juan Pablo Montoya, who won the Indy 500 here last year, was one of them in his Williams in the first session.

Benetton's Giancarlo Fisichella and Czech Tomas Enge in the Prost both ended the second session early after spinning and stalling.

Several thousand fans turned out to watch the session but the main grandstands were largely empty.

Many of the expected visitors have stayed away following hijacked planes flying into New York's World Trade Center and the Pentagon in Washington.

The daily Indianapolis Star newspaper quoted the general manager of one downtown restaurant as saying that Jaguar had cut a party of worldwide dealers on Saturday night from 350 guests to 60.

"They're worried that if the war goes on that they'll get stuck in America, in Indianapolis. Why would they come?" manager Jay Fields told the paper.

The Formula One teams showed their solidarity with America and the victims of the attacks in various manners.

Jaguar blacked out their engine covers and carried American flag stickers on them. Ferrari, who had painted their nose cones black at Monza, had Stars and Stripes on their turning vanes.