(AFP) - Budapest, Los Angeles and Paris can from Friday get tough in their race to secure the 2024 Olympic Games as they hit the final lap to the September vote.

The three rivals must hand over their third and final candidate dossiers to the International Olympic Committee but can then embark on their most aggressive publicity campaigns yet.

Frontrunners Los Angeles and Paris plan to launch into the fray straight away. Budapest is waiting until mid-February while its leaders seek to head off the threat of a city referendum on the bid.

Under new bid city rules after a series of Olympic scandals, the three cities have until now been restricted in their efforts to get to IOC members to talk up their cities.

IOC president Thomas Bach and the 100 committee members will meet in Lima on September 13 to vote the winner.

Representatives of the US, French and Hungarian bids can now aim their message at the public, use international sporting events to press their case and lobby IOC members.

They will also be allowed to use the new Olympic TV channel. IOC Olympic Games executive director Christophe Dubi said however that they will have to respect the traditional rules of not attacking their adversaries and strict equality in airtime.

The final dossier to be handed over by the rivals concentrates on the proposed legacy of their bids. It must give a firm outline of how the Games and Paralympics would go ahead and details on transport, accommodation, security and what athletes and spectators can expect.

- Legacy burden -

"In the third phase, the concept and vision are defined. This is really where cities can talk with the IOC members," said Jacqueline Barrett, the IOC's associate director for Olympic bids.

First raised in the early 2000s, the legacy chapter is now considered one of the most important parts of the Games campaign.

IOC president Bach's Agenda 2020 has sought to clampdown on excessive spending and produce Games that leave lasting facilities rather than just a two-week spectacle.

IOC members are now meant to pay particular attention to infrastructure and natural resources, human resources and the climate.

"We have learned a learned a lot from the past," said Dubi, highlighting the case of 2004 hosts Athens which spent billions of dollars on facilities that have not survived.

"The science and the social context have changed. With Athens we had difficulties to force the government to not develop permanent sites. The IOC's leverage on organisers then is not the same today. Today we ask for a legacy plan for each site which was not the case at the time."

While the 2012 London Games were considered one of the best ever -- despite the cost and difficulties to reuse the Olympic Stadium and disappointing numbers inspired to take up sport -- the 2014 Sochi Winter Games will be remembered for its $50 billion outlay. Last year's Rio Games have left a mixed memory.

Transport has been improved but the Deodoro Olympic complex has already been closed and the legendary Maracana stadium has been left in disrepair amid a legal battle over who is responsible.

Los Angeles and Paris both vaunt the fact that most of their sites are already built, with the American city even turning to stadia used for its 1984 Games.

Budapest is just making promises to provide global standard facilities.

The IOC also looks at employment, the environment and how the Games can inspire people to take up sport. These criteria are more difficult to judge for the IOC members who will hear the bid rivals at a Lausanne meeting in July, the final rehearsal before the Lima vote.

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