Istanbul, Madrid and Tokyo are making final pushes Saturday in the competition to become the 2020 Summer Olympics host city.
The International Olympic Committee votes later in the day after final presentations. The process is taking place in Argentina's capital, Buenos Aires.
With each city carrying its own major risks, the race is tight.
Political instability in Syria presents issues for Istanbul's bid in neighboring Turkey, the Spanish capital is weighed down by financial troubles, and the Japanese capital faces concerns about the crippled Fukushima nuclear plant.
All three cities have made Olympic bids before. This is the fifth for Istanbul, the third in a row for Madrid and the second in a row for Tokyo, which hosted the Games in 1964.
Top officials from each country joined the final presentations to better each city's chances of hosting the world's largest sporting event. Japanese Prime Minister Shinzo Abe and his counterparts Recep Tayyip Erdogan of Turkey and Mariano Rajoy of Spain flew to Argentina's capital, Buenos Aires, straight from the G20 summit in Russia.
Hosting the Olympics can be a huge boost for a city, bringing in massive amounts of tourism revenue and creating an opportunity for a prominent place on the world stage.