MONZA, Italy (AP) - A day after FIA kept alive Ferrari's Formula One championship bid, Fernando Alonso knows his debut for the team at the Italian Grand Prix could prove just as decisive.

Alonso trails overall F1 leader Lewis Hamilton by 41 points with six races to go after the sport's governing body let Ferrari off without any points penalty on Wednesday for breaking the team orders rule.

Alonso says he'll be aggressive in Sunday's 53-lap race. That race and the upcoming Singapore GP likely will decide Ferrari's season.

"Obviously there are less races to the end of the championship, (so) more problems you have if you have a bad weekend," Alonso said Thursday. "Monza is an important weekend and Singapore as well, and a DNF in the race will be our last chance and a goodbye to the championship."

The FIA upheld the $100,000 fine after Ferrari driver Felipe Massa let Alonso overtake him to win the race. The council could have stripped Alonso of the victory or docked the team points.

"You have to respect it and stay calm," Alonso said. "That's the past for us, we just have to focus on Monza."

Alonso commended the decision to clarify the rule on team orders.

Despite a barrage of questions about the issue, Alonso refused to delve into the subject and instead preferred to focus on the Italian GP, which begins with Friday's double-practice session.

"We should be competitive here," said Alonso, who crashed out in the last race, a wet Belgian GP. "We (have made) some changes, some analysis of what happened in Spa and I think we understood what happened. I think we have a better package."

Having described his first year at Ferrari as the best of his life, Alonso denied it would be a "disaster" if he didn't win the title.

"For sure, (it would be) a disappointment for yourself and the team," the two-time world champion said. "But the word 'disaster' is a little too extreme. It's a very competitive sport."

Hamilton has 182 points to lead second-place Mark Webber of Red Bull by three points. Sebastian Vettel, Jenson Button and Alonso follow and are separated by 10 points.

"There's still six races to go, but it's up to the rest - Fernando, Jenson and myself - to shrink the gap," said Vettel, who has 151 points. "We've already seen different leaders at different stages, so anything can happen. There's no reason to panic."

Button believes McLaren will carry over its Belgian GP form to another low downforce circuit. Hamilton won in Belgium and Button was running second before Vettel crashed into him to end his race.

"I'm positive for the rest of the season. We're not fearing anything at the moment," said Button, who finished second to Brawn GP teammate Rubens Barrichello at Monza last year. "All you need is one race for the leaders to have a bad race. We know there are still a lot of possibilities."

While the contenders battle it out, Michael Schumacher returns to Monza for the first time since coming out of retirement for Mercedes. The seven-time champion won five of his titles with Ferrari. He is a five-time winner here, including in 2006, when he announced his retirement.

"It was a tough moment, but the right moment," said Schumacher, who languishes in 10th place, 138 points behind Hamilton. "There was no regrets then and there are no regrets now to be back again."