Jan 8 (Reuters) - After a turbulent build-up, and still under a cloud of doubt, the Africa Cup of Nations finals gets underway in Cameroon on Sunday but with the tournament’s long-term future in doubt. Africa’s support for FIFA president Gianni Infantino’s proposal to change the frequency of the World Cup to every two years threatens the Cup of Nations, which is already biennial. Africa’s 54 member associations voted unanimously at last year’s congress to back the idea of a more frequent World Cup, but without discussing how it would affect their own tournament on a packed international calendar. Now expanding to 24-teams, the Cup of Nations is proving to be a strain on resources. This edition has been twice postponed, first in 2019 when the Confederation of African Football (CAF) found the country was not ready and took it to Egypt instead, and again last January because of the COVID-19 pandemic. Cameroon had been awarded the finals in 2014 and built new stadiums in Bafoussam, Douala, Limbe and Yaounde but works on the showpiece Olembe Stadium in Yaounde have continued right up to the start of the tournament, proving a major source of concern and contention. So worried were CAF about the readiness of the venue, plus Cameroon’s general organisational preparedness, that they held an emergency meeting last month to discuss cancelling the tournament. That was also motivated by the rapid spread of the Omicron variant of the novel coronavirus and the potential impact it might have on the event but in the end it was decided, amid much disagreement, to go ahead. The timing of the tournament, in the middle of the club season in Europe where the majority of African internationals play, drew the ire of clubs who also sought its cancellation. They were concerned as well about possible quarantine for players returning from Africa to Europe once their participation at the finals was complete, which would extend the time they were away from the clubs. Managers like Liverpool’s Juergen Klopp - who has lost Mo Salah, Sadio Mane and Naby Keita - have been irritated by the fact they have to give up key players at a crucial juncture of their season. The Cup of Nations is being played in January because of the heavy mid-year rainy season in Cameroon but will revert back to a June-July slot when Ivory Coast host the next finals in 2023. The 2025 finals have been awarded to Guinea, but CAF will discuss this week whether the country is able to host the tournament.