A source told CNN that players were warned that their families would face “violence and and torture” if they did not sing the national anthem or took part in any political protest during a meeting with the Iranian Revolutionary Guard Corps (IRGC).
It came after Iranian players refused to sing the national anthem in their opening match against England.
“There are a large number of Iranian security officers in Qatar collecting information and monitoring the players,” the source added.
Their Portuguese manager Carlos Quieroz, who previously said players could protest within FIFA regulations, also held a seperate meeting with the (IRGC) after the alleged threats.
Iran and the US play each other on Tuesday in a crucial Group B match.
It came after a niece of Iran’s Supreme Leader Ayatollah Ali Khamenei has urged foreign governments to cut all ties with Tehran over its violent crackdown on protests sparked by Mahsa Amini’s death.
Farideh Moradkhani comes from a branch of the family that has a record of opposition to Iran’s clerical leadership has reportedly been jailed for speaking out against the government.
In the video, she condemned the “clear and obvious oppression” Iranians have been subjected to, and criticised the international community’s inaction.
“This regime is not loyal to any of its religious principles and does not know any law or rule except force and maintaining its power in any way possible,” she said in the video.
At least 416 people, including 51 children, have been killed in the crack down, according to the Norway-based organisation Iran Human Rights.
The death of Mahsa Amini, 22, in September - after being detained by police in Tehran for allegedly not adhering to the Islamic dress code - triggered protests across the world.