Phelps has unsurprisingly cruised to victory in the 200m butterfly final to take his tally to four gold medals in Beijing, in addition to the six medals he won in Athens four years ago.

The 23-year-old has surpassed the nine-gold-medal feat of former Olympic giants Carl Lewis, Mark Spitz, Paavo Nurmi and Larysa Latynina.

However, the relentless Phelps was not finished yet as he led the US team to victory in the 4x200m freestyle final, extending his total to 11 gold medals.

The American is on course to register another unprecedented record of eight gold medals in one tournament.

"There is still something left in the tank. I've got three races left, so there had better be something left in the tank," he said.