Michael Phelps's dream of eight gold medals was kept alive by a fingertip here today - thanks to his heroic American team-mate Jason Lezak.

As the American 4x100metres relay quartet entered the last 50m, it appeared that anchor man Lezak had too much to do to make up the gap on giant Frenchman Alain Bernard, starting a body-length behind. However, he produced a scintillating final push to touch fractionally ahead in a new world record of 3min 8.24sec.

It meant that Phelps, who had swum the first leg, had earned his second gold in as many days - and the relief at now being a quarter of the way to beating Mark Spitz's record was obvious as the American roared his delight at poolside. It was clear that he felt he owed a huge debt to Lezak, the oldest man in the US swim team.

"He was unbelievable," said Phelps. "Jason finished that race better than we could even ask for. As you could see at the end, I was very emotional."

Lezak was also praised by coach Eddie Reese, who said: "I've never seen anything like that before. Running down somebody who holds the world record and is on their game is incredible." Phelps, himself, admitted he had been motivated by the confident talk of the French quartet ahead of the final.

"We just let our swimming do the talking," he said. "We didn't react to it. It just got us fired up.

Superman's dream may have been salvaged on another busy day - he was due to swim the 200m butterfly heats later - but 75 minutes before the relay final he had actually looked human as he appeared to make heavy weather of reaching tomorrow's 200m freestyle final, finishing as fourth fastest qualifier in, by his standards, a very modest 1:46.28.

It raised the question as to whether the same event which cost him his similar quest for eight golds in Athens four years ago could again prove his Achilles heel, for in 2004 Phelps's record bid was ended when he could only finish third in the 200m freestyle final.