A boycott threat hangs over the women's 5,000m after Olga Yegorova was reinstated by athletics governing body the IAAF despite failing a drug test.

The Russian tested positive for endurance-enhancing EPO in Paris last month and was initially banned from the World Championships.

But because the French authorities failed to take a blood sample as well as a urine sample - as legally required under IAAF regulations - Yegorova has been cleared to compete in Thursday's 5000m heats.

Gabriela Szabo, defending Olympic and World 5000m champion, said earlier in the week that she would boycott the race if Yegorova were allowed to take part.

Szabo's agent, Jos Hermens, now says she will make her decision after the 1500m final, which takes place on Tuesday.

Hermans hinted that he would support Szabo if she decided to withdraw in protest.

"If I thought it was bad for her to do, I would have said, 'Maybe think it over,' but this is her feeling," he said.

"Athletes should say how they feel and what they think."

Szabo has always beaten 29-year-old Yegorova comfortably until this season.

Two years ago at the World Championships she beat her by 72 seconds and in the Olympic final last summer she finished 10 seconds clear.

'Cheated'

The urine test is designed specifically to detect the presence of EPO, the drug that many officials suspect may be used by some long-distance runners.

Each test costs around �500 to administer, and only athletes who are blood-tested in Edmonton will be given one.

Dutch-based Hermens told BBC Sport on Sunday: "We accept the technicality - that's part of the sport. But she [Yegorova] has cheated. It's proven.

"The EPO test has been used by cycling, it's been verified by the UCI (International Cycling Union) but not by the IAAF and International Olympic Committee."

Yegorova, who puts the startling improvement in her times down to being free of injury, will almost certainly be tested for EPO here.

But as the test can only show if EPO has been used over the previous five to seven days, a clean result will not prove that she has not been using EPO before arriving in Canada.

She was unable to say how her urine sample from Paris tested positive for the drug.

"I can't explain it myself," she said. "I was shocked when I heard about it."

But she has asked her critics - and particularly Britain's Paula Radcliffe - to lay off.

"What can I do about it? Maybe not eat lunch with Paula Radcliffe. It hasn't been proven that I took EPO, so that should be the end of it," said the Russian.

Runners split

British 1500m runner Helen Pattinson said she would refuse to run against Yegorova if she were in Szabo's shoes.

"Personally, I would find it hard to step on the line," she said.

But Australian Georgie Clark said she would be taking part.

"People won't remember who pulls out, they'll just remember who won it," she said.