This is a potentially significant development.
According to sources close to the rebellion against Infantino, they are now sending him a clear message: resign now and leave your position with dignity, rather than seek re-election in March.
Alongside this joint statement, I am told the three confederations have begun preliminary discussions about organising competitions among themselves, so that players can still compete even if there is a boycott of Fifa tournaments such as next month’s U20 Women’s World Cup.
Since this crisis began, Asia has been seen as a key battleground, a region that could determine whether Infantino stays in power.
Some of the 46 countries in this vast region have said they still support Infantino. But the fact that the AFC president Sheikh Salman has signed off this letter suggests he is confident that there are plenty of others who want change.
Infantino still retains the support of South America, Africa, and indeed Mexico within Concacaf. But is that enough?
If UEFA and Concacaf voted as a bloc (with a few exceptions) against him, it would only need around a third of the AFC to join them to win any vote.
But could a candidate capable of challenging Infantino and unifying the game be found?
The fact those behind the revolt are so keen for him to step down suggests they are still not sure they would have enough votes.
What is clear is that this latest solidifying of the rebellion against Infantino ramps up the pressure on him once again in world football’s unprecedented civil war.