Leicester City have been left "powerless" in their wish to register Adrien Silva before January, unless the player lodges a personal appeal.
The 2015-16 Premier League champions agreed a deal with Sporting CP worth up to €29.5million to sign the Portugal international as a replacement for Danny Drinkwater, who joined Chelsea shortly before the close of the transfer window.
Leicester reportedly missed the deadline to register Silva by a matter of seconds, meaning FIFA refused permission for the move to be completed.
After an appeal against that ruling was turned down, Leicester planned to take their case to the Court of Arbitration for Sport, but FIFA's decision not to support an expedited process has left the club's hands tied.
Unless Silva pursues and succeeds in his own appeal, he will not be registered until January 1, when the Foxes are due to host Huddersfield Town in the Premier League.
"It was our intention to submit an application to the Court of Arbitration for Sport for expedited proceedings so that the matter could be resolved as quickly as possible," a Leicester statement read.
"However, it has been made clear to us that FIFA will not support an expedited process, forcing the club to reluctantly accept the single-judge ruling of FIFA's Players' Status Committee without reasonable opportunity for independent arbitration that is timely enough to be effective.
"Our frustration at the denial of effective due process doubles our disappointment at the original outcome and while the club is now essentially powerless to continue to challenge the decision, we will continue to support Adrien in any personal appeal he wishes to undertake.
"We intend to register Adrien at the earliest opportunity. In the meantime, he will remain under our care, training with the squad under the supervision of our coaching, medical and sport science staff."
