FIFA has announced that two options in the winter have emerged as the most likely dates for the 2022 World Cup in Qatar after its medical chief warned that temperatures between May and September posed a "highly critical" risk.
A meeting in Zurich on Monday of a FIFA task force has identified January/February 2022 and November/December 2022 - though the former would clash with the winter Olympics - as the most likely options.
European clubs and leagues had proposed playing the tournament in April/May or May/June.
The significant move towards a winter World Cup followed a presentation to the task force by FIFA's medical chief who warned of a "highly critical risk" to players, officials and fans of playing between June and August, and a "borderline risk" in May and September.
Professor Jiri Dvorak, FIFA's chief medical officer, has confirmed he outlined the detailed risk factors of playing in the Middle Eastern state in the summer when temperatures can reach over 50 degrees Celsius.
Dvorak told Press Association Sport: "What I have said is that for the players, the accompanying staff and the fans the months June till August are highly critical in terms of risk, due to the climatic conditions in Qatar.
"In May and September it is borderline when it comes to the temperature of high risk but from the medical point of view it is not recommended.
"The months from October until March are actually optimal in terms of the temperature."
Dvorak added that the judgement on climatic conditions was based not just on temperature but also humidity, and the amount of radiation from the sun, and that none of the venues in Brazil for this summer's World Cup had been considered even a borderline risk.
His medical report means FIFA will feel obliged to exclude playing the tournament in any of the months judged a risk - not least because of possible legal action from players, officials or fans.
FIFA secretary general Jerome Valcke said in a statement: "We are getting closer to narrowing the dates for the FIFA World Cup to two options - January/February 2022 or November/December 2022 - but FIFA has also been asked to consider May 2022.
"We will summarise what we've heard today and provide feedback to all parties in order for them to prepare for the next meeting as we progress towards a final decision."
FIFA added that Qatar 2022 chief executive Hassan Al Thawadi had stated that the ''ideal situation'' for the Middle East ''for an all-inclusive World Cup would be for it to be held in the winter'' although it was still open to the traditional June/July dates.
UEFA has argued strongly to hold the tournament in January/February 2022 - those dates would minimise disruption to the Champions League - but that would also raise the prospect of a clash with the winter Olympics, something FIFA president Sepp Blatter has guaranteed will be avoided.
The November/December option still looks the most likely outcome but FIFA confirmed the European Clubs Association (ECA) put forward a proposal to hold the World Cup in April/May 2022 while the European Professional Football Leagues - including Premier League chief executive Richard Scudamore - suggested May/June 2022 as an alternative.
The FIFA statement added: "Representatives were given the platform to provide detailed reports on how these proposed dates might impact their relevant competitions, activities and/or stakeholders. Additionally, presentations suggesting April/May 2022 and May/June 2022 as alternative periods for the FIFA World Cup were given by the ECA and the EPFL respectively."
The clubs' and leagues' proposals may well founder on the fact that the build-up would clash with the month-long period of Ramadan.
The FIFA statement said: "Valcke also highlighted the fact that the month-long period of Ramadan would begin on 2 April in 2022, which would have an impact on a number of players in their preparations for any April/May option and with regard to the preparation of the event itself."