RIO DE JANEIRO, Brazil (AFP) — With yesterday marking 500 days to go before it stages South America’s first ever Olympic Games, Rio is straining at the leash to be ready — but a key target of dealing with pollution in the bay hosting sailing events is floating out of reach.

In having to overhaul crumbling infrastructure, polluted waters and protests, notably over the choice of a nature reserve to host the return of golf to the Games, organisers could almost be forgiven for seeing the undertaking as one mammoth discipline — a giant obstacle course.

Last April, International Olympic Committee (IOC) Vice-President John Coates slammed preparations as the “worst ever” and warned “the situation is critical on the ground” following several inspection visits.

Organisers responded by creating a task force to monitor progress, and IOC President Thomas Bach insisted he was “very satisfied” following last month’s three-day meeting of the IOC’s executive committee in Rio.

Although city mayor Eduardo Paes made combative comments yesterday praising the city’s efforts to get ready, he admitted to concern over the Games’ environmental impact.

Green campaigners and athletes alike have slammed yachting site Guanabara Bay, picturesque, but a smelly dumping ground for refuse amid an ongoing struggle to clean up waters which biologists say also risk contamination from superbacteria in adjoining rivers which are resistant to antibiotics.

State authorities admit Rio will struggle to meet its pledge to treat 80 per cent of the raw sewage which floats into the bay, offering a stark contrast to the postcard image organisers offered up to mark 500 days in depicting Olympic mascot Vinicius perched atop the Sugarloaf Mountain cable car.

Paes himself admitted dissatisfaction over the bay clean-up, originally supposed to be total, then reduced to clearing 80 per cent of raw sewage, that now appearing more wishful thinking than a target with only around 49 per cent reached to date.

“As a Rio resident I think it is a shame Guanabara Bay has not been totally cleaned up. I think it is a missed opportunity,” Paes told SporTV Monday, while insisting competitor health would not be at risk with the Games being held in the cleanest part of the bay.

“Cleaning up the bay is an important legacy objective,” organisers told AFP in stressing the infrastructural and environmental legacy is “the primary focus” 17 months out from the August 5, 2016 opening.

The siting of the Olympic golf course in an ecological reserve has also enraged green campaigners, furious at the potential effect on wildlife.

Yesterday, Paes insisted the operation to build the course involved recovering a “totally degraded” area.

Paes also told SporTV the Olympics would greatly benefit urban mobility in Rio as new rapid transit bus services and a light rail system come on stream — although a new metro line is only scheduled to open weeks before the Games begin.

“Everybody knows Rio has many problems and won’t be perfect in 2016 — but it will be much better,” said Paes, who insisted the 37 billion reais (US$11.8 billion) bill has been carefully costed with around half private cash.

A total of 7.5 million Games tickets will go on sale on the official website www.rio2016.com from March 31 with prices ranging from 40 reais (US$13) to 1,200 (US$383).

Those who have registered online over the past month will from next Tuesday be able to buy with some two-thirds of tickets expected to be distributed in July and August lotteries.

A full programme of test events involving 7,800 athletes was unveiled last week, as Sao Paulo’s Corinthians Arena was confirmed as one of seven football venues in six cities, including Manaus in Amazonia.