Rio de Janeiro, Aug 11 (IANS): Michael Phelps described his rivalry with Ryan Lochte as "special" as the US teammates prepare to go head-to-head in another Olympic swimming final on Thursday.

Phelps qualified fastest for the 200m individual medley decider with a time of 1 minute 55.78 seconds in his semifinal at the Olympic Aquatics Stadium on Wednesday, Xinhua news agency reported.

Lochte finished half a second behind him with Brazil's Thiago Perreira third in 1:57.11.

"You know the history him and I have had with one another is something special and something I have never had in another competitor of mine. We have been racing for the last 12 years and having one more battle tomorrow, it will be fun," Phelps said.

"I consider Ryan and I have probably grown closer as friends this year than we have in the past, so we will have one more time to hop in the pool and duke it out," he added.

Phelps, the most decorated Olympian in history with 21 gold medals, has won each of his three finals in Rio so far: the 200m butterfly, the 4x100m freestyle and the 4x200m freestyle.

On Thursday, he will be aiming to become the first swimmer to win the same event at four consecutive Olympic Games.

Al Oerter (discuss) and Carl Lewis (long jump) are the only athletes to have achieved the feat.