ANCIENT OLYMPIA, Greece - Azeri capital Baku's 2020 summer Olympics bid is growing stronger by the day thanks to a billion-dollar investment in sport infrastructure fuelled by the country's large oil and natural reserves and the race's unexpected twists and turns, officials say.

"Every day the bid is getting better because we become more confident and there is more value to it," Azeri sports minister Azad Rahimov told Reuters on the sidelines of the London 2012 Olympics torch-lighting ceremony in ancient Olympia.

Baku is up against Tokyo, Istanbul, Doha and Madrid with the International Olympic Committee (IOC) announcing a shortlist of candidates later this month. The IOC will elect the winning bid at their 2013 session in Buenos Aires.

Initially seen as the clear outsider, Baku is bidding for the second successive time after falling at the first hurdle for the 2016 Games. It now looks in a stronger position than a few months ago as the race has been thrown wide open.

One of the early favourites, Rome, pulled out in February, due to the country's efforts to head off a debt crisis.

Madrid, bidding for the third straight time, is faced with a potentially tough situation as Spain slipped into recession in late April and is struggling with a big public deficit.

Turkey has decided to also bid for the Euro 2020 soccer championship, triggering concerns about whether Istanbul can host two huge events in a span of two months.

The IOC has said that, while there is nothing in its charter to forbid such a double bid, it would ask Turkey, sole bidders so far for the Euros with a deadline of May 15, to hand back the football tournament if it should be awarded the Games as well.

Rahimov said Baku had invested more than a billion dollars in sports venues in the past 10 years and seen financial growth shoot up by 900 percent over the same period, largely due to its energy reserves.

"It seems people have changed their minds about Baku. I see a different reaction nowadays that they know the country and the city better.

"We hope to have a chance to be in the race until 2013 in Buenos Aires."

Muslim Baku would also open up the Games to a new territory, as Rio de Janeiro will do as the first South American host in 2016.

"I think the Olympics will be all the time in new regions," Rahimov said. "I was happy that Rio won."