Michael Schumacher is on the verge of a record-breaking sixth World Championship after triumphing in a wet-and-wild United States Grand Prix at Indianapolis today.

The German needs just one point from the season finale in Japan in two weeks time after winning by over 18 seconds in his Ferrari from McLaren's Kimi Raikkonen, who is now his only threat after Juan Pablo Montoya blew his chance.

Raikkonen has to win at Suzuka and hope Schumacher's Ferrari brakes down or the German spins out if he is to become the youngest champion in history after gallantly grabbing second spot in a rain-affected 73-lap race.

Montoya had a nightmare afternoon, silencing the thousands of his fellow Colombians who had partied in Indianapolis all weekend before swelling the crowd at the Motor Speedway to a massive 150,000, easily the biggest of the season.

The Williams-BMW driver made a dreadful start, had to serve a stop-go penalty for pitching Ferrari's Rubens Barrichello into a gravel trap and ended up one lap down after sliding off as he struggled with dry tyres when the race was hit by a heavy shower.

Montoya's desperation to atone for his poor getaway as he dropped from fourth to seventh sent him darting down the inside of Barrichello when there was just not enough room, and the race stewards hit him with a penalty.

The 28-year-old found himself two laps down at one point and though he eventually finished sixth, the Colombian fell 10 points behind Schumacher and out of contention even if he won the last race.

Schumacher - with five titles already under his belt - kept his composure when the pressure was really on and his sixth victory of the season should see him eclipse the record he shares with Juan Manuel Fangio when he gets to Japan.

The 34-year-old - who also holds the mark for most wins, fastest laps and points in Formula One history - will surely linger even longer in the record books than the Argentinian who dominated the sport in the 1950's.

The early rain caught out all the title rivals as it suddenly intensified, with Schumacher pitting on successive laps while Raikkonen also had to make two stops in quick succession.

When the rain finally eased, it left Jenson Button an unlikely leader from Sauber's Heinz-Harald Frentzen, while rookie Justin Wilson was also running third at one stage for Jaguar.

Schumacher, in contrast to Montoya, made an excellent start from a lowly seventh spot and was fourth at the first corner after he got past Barrichello.

The German dropped several places to sixth in the space of two laps as as he struggled with his tyres in the drizzle, finding himself behind Raikkonen - who had sped away from pole - and Montoya.

But Montoya's problems - the 28-year-old totally lost his composure as he found himself being lapped twice - and the heavier rain was more to Schumacher's advantage as he arrowed in on that record sixth title.

The Swiss-based racer grabbed third spot from Raikkonen on lap 28, quickly reeled in Frentzen before powering past the BAR of Button at the start of lap 38 to grab the lead.

Button's hopes of scoring that elusive maiden podium finish were left in tatters a few laps later when his Honda engine blew on the home straight bringing an end to his excellent race.

That enabled Raikkonen to inherit one place, but he had to get past the Ferrari-powered Saubers of Frentzen and Nick Heidfeld to grab second spot and keep his title hopes alive - albeit hanging by the thinnest of threads going into the final in Suzuka in two weeks time.

The 23-year-old Finn, hoping to become the youngest driver in World Championship history to win the title, was well adrift of the duo, though they both had to make further pit-stops.

Raikkonen took Heidfeld when he went into the pits and then chased after Frentzen before forcing his way past him at the start of lap 55 having been 40 seconds adrift at one point.

Frentzen eventually finished third with Jarno Trulli fourth for Renault, Heidfeld fifth and Giancarlo Fisichella seventh for Jordan - his first point since winning the third race in Brazil.

Rookie Wilson boosted his chances of a full-time driver with Jaguar next season when he claimed his maiden point with an excellent eighth spot and first finish in four starts since switching from Minardi.

McLaren's David Coulthard roller-coaster race ended in retirement after a promising start, while Ralph Firman's return to the cockpit after missing the last two grands prix also ended early when his Jordan broke down on lap 52 having lost his front wing in a first-corner collision.