Brasilia - FIFA secretary general Jerome Valcke on Thursday said the organisation had to learn from delays which have posed a series of headaches in the run-up to the World Cup in Brazil.
"It is a lesson and definitely we will act differently and will have to find a different way of working for future events, starting with Russia in 2018," Valcke said after a Local Organising Committee meeting in Rio.
Late delivery of stadiums has bogged down the process of readying 12 venues across a continent-sized nation with poor transport infrastructure.
Attempts at boosting urban mobility and giving a huge facelift to creaking airport infrastructure as some 600 000 foreign tourists prepare to fly in ahead of the June 12 kickoff have advanced only slowly.
In addition, three stadiums are yet to be completed and there are concerns over who foots the bill for temporary facilities which neither local authorities nor stadium owners want to pay.
FIFA's insistence they must pay up has helped to produce a double bind in Sao Paulo, which is slated to host the opening match between Brazil and Croatia on June 12.
A fatal accident in late November put back construction which was already behind schedule at the ground owned by local club Corinthians, and the venue is not now due for delivery until mid-May.
Adding to the problems is the fact that Corinthians say they are not liable for some $20 million of investments in temporary facilities such as media work rooms.
That issue has also made waves in Porto Alegre in the south, where state lawmakers Tuesday passed a proposal offering tax breaks to companies helping to pay an $11m bill.
With the stadiums at Curitiba and Cuiaba not finished Valcke indicated that in future a new approach to funding should be considered.
With allegations of corruption clouding the award of the next two tournaments to Russia and Qatar, the countries hosting the 2018 and 2022 tournaments, Valcke used unequivocal language on Thursday.
"We are late, we face difficulties and risks right up to the last minute because we haven't tested the installations, we need time to test them," Valcke said.
On Sao Paulo, Valcke admitted: "We don't yet have a solution," though he added he was "quite confident" one would emerge by Friday.
"We will have 12 host cities; we will have 12 stadiums," he stressed. "But there is work to do. Time is flying."
Brazilian Sports Minister Aldo Rebelo insisted the authorities were lending their full support.
"We are helping so that the town hall, the state government and the (private) owners of Corinthians Arena find a solution," Rebelo said.
Corinthians chairman Mario Gobbi told Esdado de Sao Paulo late Thursday there was no cause for alarm.
"Everyone can stay calm because the bill will be paid and we will have the Cup in our stadium. We just don't know yet how it will be paid."
Earlier this week, Brazil's Development Bank released the first two-thirds of a $160m loan to complete the stadium project ready for handover by mid-May.
Despite the tight timetable, Valcke said on the basis of talks with constructor Odebrecht he was confident.
"I have full trust in Odebrecht to deliver on time for the opening game," Valcke told reporters at Rio's Maracana Stadium, which will host the July 13 final.
However, initial agreements for the host cities do not make Odebrecht responsible for the cost of the work but rather Corinthians as the owner.
Valcke insisted Sao Paulo would definitely stage the curtain-raiser.
"It will happen in Sao Paulo - there is no other choice" even if "we will maybe be a bit borderline."
On Porto Alegre, Valcke said the next three weeks were crucial as FIFA deals with various contractors rather than a solitary one as in Sao Paulo.
Brazil may be the most successful nation in the tournament's history, but the giant nation's first World Cup in 64 years has turned into a hot potato for organizers and the government.
Protest groups aghast at the spiralling cost beyond $11bn - and with the 2016 Rio Olympics to come - have promised to disrupt the tournament and several hundred people marched and waved anti-Cup banners Thursday evening in Sao Paulo and Rio.