While that has not officially happened at this point, minds at FIFA must now address more urgently the prospect of having to replace the Iranians in the tournament kicking off in the U.S., Mexico and Canada in early June.

Donyamali said it would be impossible for Iran to take part after air attacks launched by the U.S. and Israel on 28 February killed Iran's Supreme Leader Ayatollah Ali Khamenei, triggering a region-wide conflict that shows no sign of abating.

While it always seemed counter-intuitive that Iran would take part in a World Cup while at war with one of the co-hosts, FIFA was on Wednesday still clearly banking on Team Melli lining up for their first group game against New Zealand in Los Angeles on 15 June.

Only a few hours before Donyamali's statement, FIFA chief Gianni Infantino trumpeted an assurance from Trump that Iran was "welcome to compete in the tournament in the United States".

A withdrawal would be governed by Article Six of the World Cup regulations which, while stipulating a series of financial penalties for such a move, also states that FIFA would be at liberty to call up any nation it chooses to fill the void.

"There's no modern precedent for this and, according to FIFA's own tournament regulations, they have full discretion to do whatever they want in the case of a team withdrawing," James Kitching, FIFA's former Director of Football Regulatory, told Reuters.

"That means, for example, a team that withdraws wouldn't have to be replaced by a team from the same confederation, or even replaced at all. Whether either of those scenarios would be politically tenable is a different question.

"The tournament regulations also provide disciplinary sanctions for any federation whose team withdraws. However, if Iran withdrew for any reason related to this current conflict, I doubt FIFA would impose any sanctions given the circumstances."

The Iranians qualified for a fourth successive World Cup by topping Group A in the third round of Asian qualifying last year and a replacement from the world's most populous continent would make most sense, even if that is not as straightforward as it may seem.

Iraq is due to participate in the intercontinental playoffs in Mexico this month for a spot at the finals while United Arab Emirates, which lost to the Iraqis in an eliminator in November, has been mentioned as a potential candidate.

The travel freeze in the Middle East caused by the conflict is impacting Iraq's ability to get to Mexico and prepare for its match against either Bolivia or Suriname on 31 March.

Iraq coach Graham Arnold has proposed FIFA postpone that fixture until closer to the finals, saying that would be fair to the Iraqis and allow the Iran situation to play out further.

"Let Bolivia play Suriname this month and then a week before the World Cup, we play the winner in the US - the winner of that game stays on and the loser goes home," Arnold said.

"In my opinion, it also gives FIFA more time to decide what Iran is going to do. If Iran withdraws, we go into the World Cup and it gives the UAE, who we beat in qualifying, the chance to prepare for either Bolivia or Suriname."

FIFA has yet to comment on Donyamali's statement while a source at the Asian Football Confederation said it "is closely monitoring the situation and remains in contact with FIFA" over the potential replacement of Iran.

"Matters relating to the World Cup fall under FIFA's remit," the source said. "At this stage, it would be premature to speculate further."

World Cup places are much coveted by the confederations, however, and it is likely that the AFC would lobby hard for the replacement to come from Asia.

With Europe's final participants in the World Cup also decided at the end of March, Kitching believes FIFA will not make any firm decisions until early April.

"I would expect a decision is not going to be made until after the final playoffs are finished and for FIFA to take a pragmatic and consultative approach to the situation," he said.