Soccer's world governing body also warned size could be a worry in the United States, Australia and Russia as it published its evaluation of the bids to host the 2018 and 2022 World Cups.

FIFA expressed concern that television income could be reduced if the 2022 tournament was held in the Far East or Australia and questioned the idea of co-hosting in a set back for the Spain/Portugal and Belgium/Netherlands bids for 2018.

England, Russia, Spain/Portugal and Belgium/Netherlands are bidding to host the 2018 World Cup while Japan, South Korea, United States, Australia and Qatar are candidates for 2022.

FIFA will choose both hosts in Zurich on Dec. 2.

FIFA's summary on Qatar's bid began with praise for its green credentials but said holding the World Cup in such a small country could be a problem.

"The fact that ten out of the 12 stadiums are located within a 25-30 kilometer radius could represent an operational and logistical challenge," said FIFA's report.

"Any delay in the completion of the transport projects could impact FIFA's tournament operations. Moreover, it appears to be difficult to test a transport concept prior to the event under conditions comparable to the World Cup."

But the midsummer heat appeared to be the real worry.

"The fact that the competition is planned in June/July, the two hottest months of the year in this region, has to be considered as a potential health risk for players, officials, the FIFA family and spectators, and requires precautions to be taken," added the report.

On Russia, FIFA said: "The country's vastness and its remoteness from other countries, coupled with the fact that the high-speed railway network is limited... would put pressure on the air traffic infrastructure, potentially causing transfer challenges in view of the lack of alternative means of long-distance transport." The reports also said the United States and Australia were over-dependent on air transport.

On the joint bids, the report used the same phrasing.

"It should be noted that a co-hosting concept could pose challenges regarding the joint-operational delivery of the World Cup in terms of ensuring consistent standards and implementation in various areas such as legal, IT, frequencies, safety and security.

"Therefore, in order to provide a more complete basis for evaluation of the co-hosting concept, further key operational details would be required, especially in view of the administrative, logistical and financial challenges of co-hosting the World Cup."