Buenos Aires - Fears over radiation from the stricken Fukushima nuclear plant and fall-out from the bloody civil war in Syria are hanging over Tokyo and Istanbul's attempts to host the 2020 Olympics, amid suggestions that third candidate city Madrid could benefit.
Tokyo's bid leaders were on Wednesday forced to assuage lingering doubts over safety in the Japanese capital, with radioactive water leaking into the ocean, two-and-a-half years after the nuclear disaster.
Bid president Tsunekazu Takeda even revealed that he had written to every member of the International Olympic Committee (IOC), to try to allay fears.
"The water is safe and the level of radioactivity is absolutely safe," he told a news conference in Buenos Aires, where International Olympic Committee (IOC) members vote on Saturday to decide the 2020 host city.
"Our prime minister [Shinzo] Abe has officially announced that the government will be responsible for the project [to clear up Fukushima].
"I am not worried about the Tokyo 2020 bid."
But the 2011 meltdown at the plant 220km from Tokyo, which followed a devastating earthquake and tsunami that killed more than 18 000, could still be a deciding factor in the vote, according to one analyst.
Wolfgang Maennig, a sports economics specialist from Hamburg University, said the brutal civil conflict in Turkey's neighbour Syria, which has seen more than two million people flee the country, according to the United Nations, could also sway members away from choosing Istanbul.
"To my astonishment, it seems like it's going to be Madrid," he was quoted as saying by the Huffington Post on Wednesday evening.
"I talked today to the president of a national [Olympic] federation and people are still afraid of Syria and even Iraq, even though that was years ago, affecting Turkey.
"There are also many concerns about the level of radiation in Japan."
Maennig, a former Olympic rower who won gold for West Germany in the men's coxed eights in Seoul in 1988, added that he favoured Istanbul but they "lost their credibility with the protests" sparked on 31 May by an environmental battle to save a park from redevelopment.
The protests - and the heavy-handed crackdown that followed - escalated into mass displays of anger against Prime Minister Recep Tayyip Erdogan, tarnishing Turkey's image abroad.
Istanbul is also facing up to a slew of positive dope tests among Turkish athletes, although the country's sports administrators maintain that the high number of cases - 31 - is down to better and more comprehensive testing.
Intensive lobbying is expected in the run-up to Saturday's vote but Madrid, which hopes that a successful bid could kick-start a recession-hit economy, saw their momentum briefly stopped by an apparent leak of IOC voting intentions.
Spanish paper El Mundo published names - some with photos - of up to 50 IOC members who were going to vote for them.
While 50 votes would give Madrid an unlikely win in the first round of voting, the revelations did not sit well with the members, who vote in a secret ballot.
History suggests it can rebound as Le Parisien newspaper did a similar thing before the vote on the 2012 Games hosts in 2005, which saw London edge out Paris in a shock result.
One senior IOC member said the revelations in El Mundo had gone down "like a lead balloon" with the members.
But outgoing IOC President Jacques Rogge, whose successor will be appointed next Tuesday, said he did not believe that Madrid would suffer from the revelations.
"I would say that one shouldn't pay any attention or give credit to this type of information," said the 71-year-old, who has been at the helm for the last 12 years.
"Only the person who presses the button [the way the IOC members vote] on Saturday knows how they are going to vote.
"It won't harm Madrid's bid because my colleagues don't give this type of information any credence either."