Female fans at an Asian Cup semi-final match in January 2019

Fifa president Gianni Infantino has written to the Iranian Football Federation to seek assurances that women will be allowed to attend 2022 World Cup qualifiers.

In a letter seen by BBC Sport, Infantino also expresses his disappointment that Iran has gone back on its commitment to open up stadiums.

Last October, female fans were allowed into a match in Tehran for the first time following a 40-year ban.

In November, hundreds of women also attended an Asian Champions League final match which saw local team Persepolis lose to Japan's Kashima Antlers.

But Infantino said in the letter it was "disappointing" to learn that fans were turned away from Iran's friendly match with Syria on 6 June and that a number of fans were detained by authorities.

Writing to Iranian Football Federation president Medhi Taj, he said: "This is not in line with the commitments given to us in March 2018 by [Iran] President Rouhani when we were assured that important progress would be made on this matter soon.

"Whilst we are aware of the challenges and cultural sensitivities, we simply have to continue making progress here, not only because we owe it to women all over the world, but also because we have a responsibility to do so, under the most basic principles set out in the Fifa statutes.

"In the circumstances, I would be very grateful if you could inform Fifa, at your earliest convenience but no later than 15 July 2019, as to the concrete steps which both the FFIRI [Football Federation Islamic Republic of Iran] and the Iranian state authorities will now be taking in order to ensure that all Iranian and foreign women who wish to do so will be allowed to buy tickets and to attend the matches of the qualifiers for the Fifa World Cup Qatar 2022, which will start in September 2019."

Infantino's letter comes after Fifa admitted it was wrong to eject two fans from a Women's World Cup match in France for wearing T-shirts calling for Iranian women to be let into stadiums.

Fifa said the message was "social, not political" so not against its rules and added it "will do its best to ensure similar situations do not occur at future matches".