Iran's allocation of fan tickets for the group stage of the World Cup has been revoked just days before the start of the tournament, says the country's football federation.

The World Cup, co-hosted by Canada, Mexico and the United States, begins on Thursday, with Iran scheduled to play New Zealand on 15 June and Belgium on 21 June - both in Los Angeles - before facing Egypt in Seattle on 26 June.

Iran's governing body says Fifa regulations state each federation involved in the World Cup receives 8% of the tickets for each of their matches, to distribute to supporters.

It added that it had already begun selling tickets but can no longer provide them to fans, some of whom have already made travel arrangements.

"Depriving Iranian supporters of access to their lawful and official allocation of tickets is an action contrary to the spirit of governing international competitions and the principle of equality among participating countries," the FFIRI statement said.

"This development raises serious questions about the interference of non-sporting and political considerations in the organisation of the world's biggest football event."

The FFIRI also called on Fifa "to uphold the principles of neutrality, fairness, and established regulations".

Iran's involvement in the World Cup has been plagued with uncertainty, linked to the ongoing war in the Middle East and related security concerns.

On 25 May, Iran moved their training base from Tucson, Arizona to the Mexican city of Tijuana, claiming the US were unwilling to host them.

Under the conditions of their visas, they will have to fly in and out of the United States on matchday for each of their three group games.

Less than a fortnight later, on 6 June, they accused the US of denying visas to "integral" members of the national team's backroom staff, with 15 administrative officials denied entry.

The FFIRI had previously presented Fifa with a list of 10 conditions for their participation in the World Cup, including allowing players, coaches and officials who have completed military service with the Islamic Revolutionary Guard Corps (IRGC).

US secretary of state Marco Rubio has said Iran's players will be welcome at the tournament but individuals with links to the IRGC could face entry restrictions.

Iran were the only country not present at Fifa's annual congress in Vancouver in April after a delegation of FFIRI officials, including president Medhi Taj, were turned away at the Canadian border. (BBC)

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