"I cannot stand by while FIFA considers selling a stake in the World Cup," Cordeiro, a former Goldman Sachs banker, said in a Friday statement resigning as adviser to FIFA President Gianni Infantino that urged other senior FIFA staff to speak out.
Cordeiro often joined Infantino on working visits to meet US President Donald Trump at the White House in recent years.
"Let me be clear. I had no involvement in this proposal, and I oppose it unequivocally," Cordeiro, the former US Soccer Federation president said, calling the $US20 billion commercial subsidiary "a bad deal for football."
"Football has been central to my life, and after more than 35 years in banking, I understand both the value of this asset and the consequences of giving part of it away" he said. "That is why this proposal should be rejected."
Infantino has proposed spinning off FIFA's commercial businesses — including World Cups and Club World Cups for men and women — into a $US20 billion subsidiary with 20 per cent owned by private investors.
The "anchor investor," described by FIFA, is a New York-based investment firm created by Joshua Kushner, the younger brother of Trump's son-in-law Jared Kushner.
"FIFA already has access to extraordinary financial resources. The organization sits on billions of dollars in reserves and no debt," Cordeiro said, noting FIFA's revenue of $US15 billion over the last four years tied to the men's Wold Cup just ended.
"Against that backdrop, selling a permanent stake in football's most valuable asset to raise $4.2 billion makes little sense. It is mortgaging football's future without any compelling justification," he said.
Cordeiro said he shared five years working for FIFA alongside Infantino with "dedicated, principled people who care deeply about the game."
"I hope they, too, will speak up," he wrote, "because decisions of this magnitude should be made in the interests of football, not those who stand to profit from it."
Infantino has been president of FIFA for more than 10 years and had seemed sure to be reelected unopposed next March. FIFA has set a November 18 deadline for challengers to come forward.
FIFA said on Friday it would push ahead with consultations on a plan to bring private investment into the World Cup despite European football threatening a boycott and other regional confederations rebuking the scheme.
"We will proceed with this consultation process to ensure that each MA (Member Association) has the ability to express its vote based on facts," it said in a statement.
"Nobody is selling football. This is not something FIFA would ever entertain," it added.
"Everyone has the right to express their opposition and to seek further clarification but no single entity can claim to represent all 211 MAs around the world.
"Each MA should be allowed to review the proposal and have a say in shaping their own future. These are the democratic principles of FIFA."