Uefa will convene an emergency virtual session on Thursday afternoon to shape its reply to the disputed World Cup investment proposals advanced by Fifa and president Gianni Infantino.

The European body continued its criticism after learning that Fifa had circulated a letter, obtained by the BBC, to all 211 members setting a 19 September deadline for accepting the scheme and receiving the first $20m of a promised $40m payment.

"We have become aware of Fifa's ultimatum requiring associations to back the plans or lose the one-time payment," Uefa stated. "This reveals the true nature of the scheme."

This marks the body's second public statement, following an earlier claim that Fifa had "crossed a line."

Details of the virtual meeting agenda remain unclear at this stage.

Several associations, among them the Football Association, expressed anger at discovering the proposal to sell a 20 percent stake in Fifa events to private investors, fronted by Thrive Eternal and linked to Joshua Kushner, through media reports rather than official channels.

FA chairwoman Debbie Hewitt was one of the Fifa vice-presidents left uninformed in advance. Similar concerns have been voiced by the Asian, South American and North and Central American confederations.

Former FA and Manchester City chairman David Bernstein urged England to consider withdrawing from the World Cup should the proposals advance.

Three 2026 World Cup semi-finalists belong to Uefa's membership, and the body recognises that a boycott would threaten the tournament's financial foundation.

Such a step is seen as an extreme measure, especially since one member has indicated broad support for the plans.

"We recognise the practical advantages for Czech football," said Czech Republic FA president David Trunda.

Following widespread criticism of both the proposals and the process behind them, Fifa issued an eight-page document on Wednesday evening outlining its rationale.

Fifa argued that "too little of football's growing commercial value has reached the parts of the game that need it most."

Observers have noted that the amounts involved exceed the annual budgets of some associations and have questioned oversight of existing Fifa distributions in certain regions.

Infantino nevertheless maintains the funding would deliver "better pitches, stronger national teams, more pathways for young players, and greater support for women's football."

In a Fifa video released on Wednesday, Infantino described the offer as "an offer, not an obligation."

"It forms part of a democratic consultation and represents an opportunity rather than a requirement," he continued.

"It is a golden opportunity to accelerate the global growth of the game."

Fifa highlighted the first-time World Cup qualification of Cape Verde, Curacao, Jordan and Uzbekistan as evidence of progress, partly enabled by the expansion to 48 teams.

The organisation also referenced Formula 1, La Liga, Ligue 1 and the Bundesliga as models of dedicated commercial structures.

Private investors would have "absolutely no" influence over the World Cup, Fifa insisted.

Wednesday brought a series of largely critical reactions.

The European Leagues described the plans as "a reckless and divisive development for world football."

"The World Cup should not be for sale. It is not the Fifa president's private equity asset," the statement continued.

Global players' union Fifpro urged Fifa to "reconsider its proposal without further delay."

The union expressed "deep concern" over turning the World Cup and other competitions into assets for private capital.

Such a change "would fundamentally and irreversibly reshape the incentives underpinning the competitions" and the lack of transparency was "particularly troubling," Fifpro added.

La Liga president Javier Tebas accused Infantino of attempting to secure votes ahead of the next Fifa congress in March.

"It does not appear to be a reform. It resembles an electoral campaign funded by football's future," Tebas remarked.

"Development must not be used to purchase votes or silence. The competitions and commercial rights of Fifa are not Infantino's personal property.

"Whoever blends politics, discipline, money and power without transparency cannot lead anything.

"Infantino is not the solution to Fifa's governance. He is the problem."

Hans-Joachim Watzke, vice-president of the German Football Association and Borussia Dortmund president, told Kicker magazine that the plans represent "an absolute attack on football."

"A line has been crossed here. If European football stands united against these plans, that carries a great deal of weight," he said.