Ian Thorpe [File photo]

Five-time Olympic champion Ian Thorpe has warned Australians not to expect too much of him too soon as he prepares to make his return to competition in Singapore this week.

The 29-year-old is on the comeback trail after coming out of a four-year retirement in February in an attempt to compete at next year's London Olympics.

Thorpe will be swimming in the 100m butterfly and individual medley this weekend but said fans should not be disappointed if the "Thorpedo," who once demolished world records for fun, was not immediately apparent.

"Just don't expect too much from me right now and don't judge too quickly," Thorpe told the Daily Telegraph newspaper.

"I always said that my number one intention in making a comeback was to be better than at the peak of my career. I'm not here to make up the numbers and I want to succeed.

"But Friday is just the beginning of racing again and whatever happens over the next few weeks, I'm here to swim and I won't give up. London is my ultimate goal and win or lose here in Singapore, nothing changes long term."

Thorpe has shed 10 kilograms in body weight since his return and has just completed two weeks of training at altitude in Switzerland.

"I'm coming off a pretty heavy training programme," he told the paper. "My body feels good and it's slowly dawning on me, I'm about to race again.

"But at the same time, I'm nervous because I just don't know what to expect."