The Belgian federation wants an explanation from FIFA about a decision to let United States forward Folarin Balogun play in their World Cup match on Monday despite receiving a red card in his previous game against Bosnia-Herzegovina.
On Sunday, FIFA announced Balogun would be allowed to play for the U.S. against Belgium after suspending his red card and the resulting one-match ban, an extraordinary move that triggered praise from President Donald Trump and outrage from Belgium's team.
It appeared to be the first time since 1962 that a red card during a World Cup didn't result in a suspension.
The decision prompted a furious response from the Belgium federation (RBFA) in a lengthy statement. It did not specify where it intends to appeal FIFA's decision.
And in a second statement issued on Monday morning -- just hours before the round-of-16 match between the U.S. and Belgium is due to kick off in Seattle -- the RBFA demanded more information about how the decision had been reached and denied reports FIFA had allowed Belgium to appeal.
The statement read: "After learning through media reports of FIFA's decision to lift the automatic suspension of player Balogun, the RBFA sent a letter to FIFA requesting a copy of the decision, an explanation of the process that had been followed, and setting out its position regarding the applicable regulations.
"As its only response, FIFA sent a letter to the RBFA stating that it considered this correspondence to constitute an appeal, that a judge had been appointed, and that the RBFA had only a few hours to complete that appeal. No information whatsoever was provided by FIFA.
"For an appeal to be admissible, FIFA's own regulations state that the reasoned decision must first have been communicated to the appellant. While the RBFA was merely seeking legitimate explanations, FIFA itself created an appeal and immediately ensured that it would be declared inadmissible.
"All of this occurred while FIFA simultaneously refused to respond to the RBFA's legitimate requests."
In the same statement, the Belgium federation also accused FIFA of doctoring a prematch presentation to remove the section which informed federations that any player receiving a red card would face an automatic one-match ban.
They said FIFA's decision and a lack of clarity about how it had been reached had given them no choice but to "challenge the player's eligibility for the upcoming match."
The statement continued: "During the match coordination meeting, FIFA deliberately removed the section concerning the automatic suspension of players from its presentation.
"This topic had nonetheless been part of all such meetings before each of the previous four matches. The RBFA questioned FIFA, both orally and in writing, about the reasons for this change, yet once again received no response.
"To be clear, as of this moment, the RBFA has still not received any decision or any explanation from FIFA regarding this matter. It therefore has no alternative but to challenge the player's eligibility for the upcoming match.
"Regardless of the sporting outcome of this match, the RBFA is deeply concerned by the course of events and will continue to fight in the coming hours, days and months in defence of the fundamental principles of ethics, fair competition, and the interests of football as a whole."
President Trump on Monday took credit for getting FIFA to review the red card issued against Balogun but said he did not demand an outcome.
"All I did was ask for a review," Trump said when asked about it during an unrelated Oval Office media briefing. "I didn't say, 'You have to do this.'"
On Monday, FIFA president Gianni Infantino issued a statement confirming he spoke with Trump but insisting that "FIFA's judicial bodies are independent" and that Infantino had no influence in the FIFA decision regarding Balogun.
A U.S. official said on Monday: "The president and Infantino did speak, and the president wanted to better understand the reason why a red card was given and why there was a suspension. The appeal process is run by an independent board. The U.S. government provided additional evidence that was used in the appeal process. Ultimately the correct and proper outcome was achieved."
In a statement issued by UEFA on Monday, the European governing body said the decision had "crossed a red line" and expressed "disbelief at such an unprecedented, incomprehensible and unjustifiable decision."
The fallout from FIFA's decision Sunday included Belgium coach Rudi Garcia saying in a news conference that "I didn't know that at the World Cup, the fifth of July is actually the first of April -- it's April Fools."
Belgium take on the USMNT later Monday for a spot in the quarterfinals.
Balogun, the U.S. star with three goals in the tournament, received a red card for stepping awkwardly on the right ankle of Tarik Muharemović of Bosnia-Herzegovina in a 2-0 round-of-32 win on Wednesday, triggering an automatic one-game suspension.
Information from The Associated Press and ABC News contributed to this report.