Iran's football federation complained to Fifa over the issue.

"Sometimes things are out of our control," Berhalter said on Monday.

"We're not focused on those outside things and all we can do is apologise on behalf of the players and the staff, but it's not something that we were a part of."

The US and Iran cut diplomatic relations in 1980 and the meeting of the two nations in the World Cup comes amidst a backdrop of widespread anti-government protests in Iran.

Iran has accused the US and other foreign adversaries of instigating the protests, with the US government imposing sanctions on Iranian officials over the crackdown.

The US said they decided not to use Iran's official flag in the social media posts to show "support for the women in Iran fighting for basic human rights", amid mass anti-government protests in the country.

The protests in Iran, met with a fierce crackdown, have been sparked by the death in custody in September of Mahsa Amini, a 22-year-old woman who was detained by morality police for allegedly breaking the strict rules around head coverings.

A US Soccer spokesman later said the posts had been removed and replaced with ones using the correct Iran flag, but added: "We still support the women of Iran."

Berhalter said: "We had no idea what US Soccer put out. The staff, the players, we had no idea. For us our focus is on this match and I don't want to sound aloof, or we're not caring by saying that.

"Of course are thoughts are with the Iranian people, the whole country, and everyone. But our thoughts are only on this match."

Both the United States and Iran go into Tuesday's match knowing they will definitely go through to the World Cup last 16 with a win, but will be eliminated if they lose. A draw would knock out the US, and leave Iran relying on Wales not beating England.

The two teams last met at the World Cup in 1998, with Iran winning 2-1, but both teams going out in the group.