The cities bidding to host the 2020 Olympics and Paralympics have made their presentations and described why they should stage the Games.
Istanbul, Tokyo and Madrid are the contenders in a secret ballot that will be announced at 21:00 BST on Saturday.
Turkish city Istanbul was the first to reveal its presentation at a meeting of International Olympic Committee (IOC) members in Buenos Aires, Argentina.
Tokyo's bid was shown second, followed by the Madrid presentation.
IOC members will also decide on Sunday which one of squash, baseball/softball (joint bid) or wrestling will be added to the Olympic Games programme in 2020.
And a new IOC president will be elected to replace the outgoing Jacques Rogge.
The Turkish presentation, Istanbul's fifth bid for the Olympics in the past 20 years, focused on linking Europe and Asia together, with importance placed on the country's ancient history and the multi-cultural population.
Istanbul's campaign had suffered a setback from political protests this summer - some at proposed Olympic venues - and also a series of doping scandals among the country's athletes. But the bid presentation highlighted the strength of the country's economy, the ambition to inspire future athletes and the prospect that the Games would bring peace to the region. It also repeatedly referenced "zero tolerance to doping".
Turkish Prime Minister Recep Tayyip Erdogan said: "To decide to host the Olympic Games in Turkey, the land of youth, and in the 8,000-year-old city of Istanbul, a city where continents meet, will embody the Olympic spirit.
"It will be the bridge to link the past with the future and link continents, cities and the legacy of mankind. We see the Olympic Games as the rings of peace, sharing and respect."
Japan's bid was the second to be heard and Prime Minister Shinzo Abe insisted Tokyo was a safe place to host the Games.
After an earthquake and tsunami hit the north-east of the country in 2011, there have been concerns that the Fukushima nuclear plant, which is 150 miles from the city, is unsafe. But Abe insisted: "It has never done, and will never do any damage to Tokyo."
The presentation also revealed the role sport had played in boosting the country in the past two years and pointed out that no Japanese athlete had failed a drug test at an Olympics or Paralympics.
Sponsorship would reach record levels and 10 new permanent sports venues would be constructed, including the Olympic Stadium, which will be finished by 2019, in time to host the Rugby World Cup.
Spain's bid emphasised providing a "sensible, reliable and trustworthy" Olympics.
The presentation revealed that 80% of potential venues were already built and in use, although the delegation was also keen to stress that "Madrid is fun" and a popular tourism destination.
"This is the most responsible funding in recent Olympic history," said Prime Minister Mariano Rajoy. "Madrid can host the Olympics without any risk to the Olympic movement."
But there were further questions relating to Spain's attitude to illegal drug taking in sport, after the controversial decision by a judge that 200 blood bags from the recent Operation Puerto doping scandal could be destroyed.
"We have had a problem in the past [with doping] but we have sharpened the law," said Madrid bid president Alejandro Blanco. "We are committed to fighting against doping and we believe in clean sport."
Mike Lee, the head of Vero Communications who worked on the successful Olympic bids for London, Rio de Janeiro (2016) and Pyeongchang (winter 2018), believes there is still all to play for.
He said: "All the bid teams have been forced onto the defensive for a large part of this campaign because of a range of issues.
"It does still feel that there is a lot to play for, and the final presentations and last two days of lobbying could be very important."
A decision will also be reached by IOC members on the addition of an extra sport for the 2020 Olympics.
A space was freed when wrestling was originally dropped in February, though it was then allowed to reapply.
It remains in the running after the IOC executive board voted for it following 30-minute presentations by each international federation.
Baseball and softball were dropped as individual sports after 2008 in Beijing, but are now back as a joint bid, while squash has never been played at the Olympics, although it is a Commonwealth Games sport.
IOC president Jacques Rogge will step down on Tuesday after 12 years at the helm and a secret ballot will take place on the same day to decide from six candidates to replace the 71-year-old Belgian.