Michael Phelps won his first gold of the Olympic Games in the 400m individual medley and outdone his own world record.

The first step of his dream to eclipse Mark Spitz's seven golds in 1972 had been spectacularly negotiated and, as if to ratchet up the pressure just a touch, half the White House had turned up to cheer him on.

Up in the stands American president George W Bush waved the Stars and Stripes alongside wife Laura and dad and former president George Bush snr.

Former secretary of state Henry Kissinger sat a row in front with former Republican candidate Mitt Romney while secret service men turned the Beijing Aquatics Centre into something resembling a scene from the 'West Wing'.

The president is accustomed to being saluted. This day he had come to salute a swimmer whose name in years to come could be synonymous with Beijing 2008, just as Jesse Owens dominated the Berlin Games of 1936, Spitz the ones in Munich and Carl Lewis was the face of Los Angeles in 1984.

Phelps described the president's presence as "pretty neat" and put down the tears he shed on the medal podium to relief at having deposited the first gold successfully.

He said: "I wanted to sing on the medal podium but I couldn't stop crying. I started thinking about everything that happened this year and the ups and downs we've had.

"I was just happy to get the first one under my belt. Thinking about all that just made me more and more emotional. Having the stars and stripes, representing your country and just thinking about everything.

"Everybody's watching at home and it's just an honour to do what I did."

Stand by for more emotion as Phelps edges nearer to history this week.

Shorn of his beard and moustache Phelps might resemble a rather bland-looking US marine, but once he pulls on his wet-suit bottoms he appears invincible.

His winning margin over Hungary's Laszlo Cseh was 2.32 seconds with US team-mate Ryan Lochte almost a further two seconds back in third.

"As soon as I turned at the 150 (metre mark), I was like 'Wow we're really tight together'" Phelps said. "I thought 'This was going to have to be a fast 200.'"

While the critics might point to swimming's overblown programme giving 23-year-old Phelps opportunities for too many golds over too-similar distances the manner of his triumphs set him apart as an Olympian who will go down in legend.

The rhythm of his stroke, the sharpness of his turns, the lung power and final acceleration place him in the land of the greats. It would also be wrong to say his phenomenal time was beyond his wildest dreams, because that is exactly where it came from.

Phelps explained: "I had a recurring dream last night. I kept seeing three minutes and seven seconds. I told Bob (his coach Bob Bowman) and said 'Why do I keep seeing three minutes and seven seconds?' and Bob said 'You're probably thinking of that being your 300 split in the 400 IM.'"

In fact he was five tenths of a second out, recording 3.07.05 after 300m, and added: "I wanted to go 4.03 and I didn't know if I'd do it today. It hurt a lot more than I thought it would. I'm almost shocked that I went that fast."

The challenge now is to to keep peaking for seven more events. Phelps, however, believes he can cope with the pressure.

He said: "This is probably the best shape of my life. I've dropped about two and a half seconds in the last year.

"I'm not downplaying this race, but I have to put it behind me. I have to just act like it never happened. I have so many top races ahead."

Afterwards, Phelps announced that this would be the last time that he raced in the 400 IM - arguably his toughest event - because he wants to try out new distances.

"I told (coach Bob Bowman) that this would be my last 400 IM, so I've got to go out there and get a good time," he said. "And this was a good time."

Ominously for his opponents, however, he also recognised a feeling he experienced in Athens four years ago when he won six golds and two bronzes to narrowly miss out on a 1m bonus offered by sponsors Speedo, a fortune on offer again if he can beat that Spitz record.

Phelps said: "The last 25 to 50m in Athens I saw myself out there and smiled.

The first gold was there and I had the same feeling here. I was hurting but I started smiling."

Phelps booked his place in the semi-finals of the men's 200m freestyle by finishing second in the final heat behind Switzerland's Dominik Meichtry, who won in 1:45.80.