BEIJING, August 10, 2008 (AFP) - Michael Phelps opened his bid for Olympic history in scintillating style Sunday, smashing his own 400m individual medley world record to claim the first of a possible eight gold medals at the Beijing Games.

With US President George W. Bush in attendance at the futuristic Water Cube aquatic center, Phelps outdueled Hungarian Laszlo Cseh and fellow American Ryan Lochte to win in 4min 03.84sec - slicing 1.41sec off the previous world mark of 4:05.25 he set at the US trials in June.

'I am pretty happy about that, that was a pretty emotional race today,' said Phelps, the subject of intense scrutiny for months as he readied his assault on US swimmer Mark Spitz's record of seven gold medals at one games, set in Munich in 1972.

Phelps was unable to match Spitz's feat in Athens four years ago, winning six golds and two bronze. But he raised expectations that he could go even one better in Beijing when he won seven titles at the world championships in Melbourne last year.

To do so, he'll have to swim at least 17 times over the nine days of competition at the Water Cube as he goes for gold in five individual events and three relays.

On Sunday evening he was due to swim heats of the 200m freestyle, in which he finished third in Athens but has since claimed the world record.

Phelps signalled his intentions early, with a blistering opening butterfly leg. He briefly surrendered the lead to Lochte at the first turn of the backstroke, but regained a narrow margin heading into the breaststroke.

'I knew it was going to be a tough race all the way through, I wasn't really happy to turn and see all three of us together at the 200 metres point,' Phelps said. 'I wasn't really comfortable with that close a race, I normally have more of a gap.'

Lochte, swimming two lanes over, briefly edged ahead on the first breaststroke length, but Phelps held the advantage at every remaining turn, inexorably closing out his rivals with a majestic finishing freestyle.

'I made my breaststroke a bit stronger and the freestyle was all downhill,' Phelps said. 'That was pure adrenalin.'

Said Lochte: 'It was all over by the freestyle.'

Cseh, lying a close third most of the way, overtook Lochte for the silver in the final freestyle leg, clocking a European record of 4:06.16.

Lochte took the bronze in 4:08.09.

Contemplating the scoreboard as he hugged the pool wall, Phelps smiled then raised an arm in triumph. He waved again as he exited the pool to a signal of congratulations from Bush.

'It was cool,' Phelps said of the presidential salute. 'I looked up and saw him, he waved the flag and nodded his head, that was a cool feeling to have the president here and to say congratulations.'

Park Tae-Hwan claimed South Korea's first ever Olympic swimming gold with a triumph in the 400m freestyle in the second-fastest time in history of 3:41.86.

The 18-year-old sensation held off a fast-closing Zhang Lin of China, who exhilarated the crowd of some 17,000 by taking silver in 3:42.44.

American Larsen Jensen was third in 3:42.78.

Australian distance great Grant Hackett, who will be bidding for a record third straight 1,500m free title later in the week, called Park's performance 'awesome'.

'I thought it would be a 3:41 time that would win it, he did a great job,' said Hackett, who finished sixth.

'It's no big surprise, he has been improving steadily over the last few years and he swam the sort of time I wanted.'