Ian Thorpe's remarkable swimming career is hanging by a thread with Australia's most decorated Olympian set to miss the last major international meet before the 2008 Beijing Games.

The five-time Olympic champion will decide in the next 48 hours whether to compete at the world championships selection trials in Brisbane from December 3-10.

Thorpe is next to no chance of swimming at Chandler Aquatic Centre next month and he has been handed two days to work out his next plan of attack.

If he misses the trials, Thorpe rules himself out of next March's world championships in Melbourne, making his chances of a grand finale in Beijing less likely.

He hasn't competed at a major international meet since the 2004 Athens Olympics, some 27 months ago, due to a combination of motivational problems, injury and illness.

The 24-year-old's last world record was set when he was a teenager and he has struggled this year to return to his best form due to a bout of the energy-sapping glandular fever, after sitting out competition in 2005.

Australian head coach Alan Thompson called for a quick decision to be made.

"I think it is a distraction for Ian, he needs to know where he is going to go for the rest of his life and have a plan in place," Thompson told AAP.

Thorpe has plenty to consider, as immediate retirement would no doubt impact on the millions of dollars he is paid in sponsorship deals every year.

Former national head coach Don Talbot urged Thorpe to either put up or shut up.

"I think there is a deeper problem he has to make a decision about whether he really wants to swim or not," Talbot told AAP.

"If he doesn't he should make that announcement and then get out of it.

"I don't think he will lose any friends - I think a lot of people would respect him for making the decision.

"There has been some waffling of `I am in, I am out' and I think people get a bit tired of that."

Asked what swimmer had returned following such a disrupted preparation as Thorpe, Talbot replied: "I can tell you there is nobody.

"Like golfers or tennis players they can come back and play but they are only a shadow of their former selves."

Thorpe's coach Tracey Menzies and stroke guru Milt Nelms held a brief press conference on Sunday in Sydney regarding his participation in Brisbane.

They showed their support for the star charge but failed to speak with any confidence about his future.

"I think there is a level of commitment that needs to be and I just think that to take the steps you need to take there has to be that commitment factor," Menzies said.

Thorpe is renowned for his mental strength but Menzies hinted he was finding it hard to cope with the reduced energy levels caused by glandular fever.

He had a three-month sojourn in Los Angeles this year in a bid to revitalise his swimming but has missed several training sessions since returning home in October.

"As far as your health is concerned, if you are not 100 per cent it is very hard to stand up and do what you have to do day in and day out," Menzies said.

"That is the hardest thing that he is coming to terms with that physically in himself, he is not at the level that he wants to be at."

Thompson said the drama surrounding Thorpe would only be a distraction for his training mates at Sutherland in Sydney's south and not the national team as a whole.

There has been tension between Thorpe's camp and Swimming Australia in the past with the superstar's management making him a very separate entity from the rest of the Dolphins.

The Australian team competed at last year's world championships in Montreal without Thorpe and returned home with a record medal haul.

But Thorpe's absence is still a massive dent to the men's team which misfired at this year's Commonwealth Games without his or team captain Grant Hackett's services.

Menzies said Thorpe wouldn't be prepared to swim if he wasn't at his best.

"You have an athlete who has been to two Olympics so he knows exactly what he needs to step up onto the blocks to be the best," she said.

"I don't think you are dealing with an athlete that is going to step up there if he is not going to be able to give his best."

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