SYDNEY - Speculation mounted that Australian Olympic swimming star Ian Thorpe could announce his retirement from a record-breaking competitive career.

Speculation mounted that Australian Olympic swimming star Ian Thorpe, pictured March 2006, could announce his retirement from a record-breaking competitive career. [AFP\File]

Thorpe was due to address a news conference at midday local time (0100 GMT), where he was expected to at least declare that he would miss next year's world championships, the last major international meet before the 2008 Beijing games.

Australian head coach Alan Thompson said he believed Thorpe would not swim at the world championships in Melbourne, but hoped that would not signal the end of his career.

"He would not call a press conference if he was going to swim," he said.

Australian swimming team captain Grant Hackett said it wouldn't be impossible for Thorpe to mount a comeback for the Beijing Olympics.

"I don't think it's impossible, but the longer you leave it, the harder it becomes," he said.

Health concerns have restricted the 24-year-old world and Olympic champion's training ahead of the Australian world championship trials on December 3-10.

If Thorpe misses the trials he will be ineligible to swim at the world championships next March , which would impact on his chances of representing Australia at a third Olympics in Beijing.

The swimming superstar has not competed at a major international meet since the 2004 Athens Olympics, some 27 months ago.

"Ian has had a long road back from illness and he has been diligently applying himself, at least in my experience in the US, to get himself ready to swim at the worlds," coaching consultant Milt Nelms told reporters Sunday.

"It has been tougher than we thought and we're going to get together and make a decision within the next 48 hours."

Thorpe's bid to come back following a year out of competition last year has been ravaged by illness and injury.

He was ruled out of the Melbourne Commonwealth Games last March because of glandular fever and he has struggled to shake off the energy-sapping illness.