With less than three weeks to the tournament in Morocco, which runs from December 21st to January 18th, football's world governing body announced on Wednesday that clubs need only release players from December 15th instead of a fortnight before the start of a continental championship, as is the FIFA regulation.
Senegal have cancelled their planned training camp in Tunisia, sources said, while Angola, the Democratic Republic of Congo, Mozambique and defending champions Ivory Coast are having to rethink plans for preparations in Portugal and Spain.
"What's frustrating and exhausting is that since the last international window, we've been finalising the preparations," said Angola's French coach Patrice Beaumelle.
"We wanted to start the camp on December 8th in the Algarve region of southern Portugal. I've been travelling to the site for a month and a half now. We've prepared everything, worked on the content of the training sessions, and the venues for the friendly matches. Now everything is at risk.
"We have to be in Morocco on the 18th to play on the 22nd. So we can no longer call it a training camp," he added.
Several planned friendly internationals to warm up for the tournament also face being cancelled.
"We initially wanted to play two friendly matches, on December 14th and 18th, but we should only play one, against an opponent yet to be determined," said Gabon coach Thierry Mouyouma.
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The majority of the 24 countries competing at the AFCON finals draw their players from clubs in Europe, who would ordinarily have had to release them after this weekend.
FIFA said the shortened release period, the same approach used for the 2022 World Cup in Qatar, was agreed after consultations with the Confederation of African Football and other stakeholders to "reduce the impact on various parties," without elaborating.
Mali coach Tom Saintfiet, however, said it showed a lack of respect for African football and that European clubs were given a higher priority by FIFA.
The late notification was also criticised by the coaches, given that the dates for the AFCON finals were announced in June last year, giving FIFA ample time to make its ruling.