Gregg Berhalter apologised for US Soccer posting an altered Iran flag on social media but insisted he and the United States team knew nothing of it in a tense World Cup pre-match news conference.

The Group B meeting of the USMNT and Iran was always likely to be politically charged given the friction between the two countries.

In an early answer at his media briefing on Monday, Berhalter sought to head off such questions, saying: "When I think about this match, I know a lot of other constituents have a lot of feelings towards it.

"For us, it's a soccer game against a good team. It's not much more than that. It's a knockout game, both teams are desperate to go to the next round. That's how we're looking at this match."

But that did little to quell the line of questioning, which was not helped by a Twitter post on Sunday.

US Soccer uploaded an edited Iran flag without the emblem of the Islamic Republic in a move to support protestors in the country, where there has been unrest since the September death of Mahsa Amini, a 22-year-old woman who died in police custody after being arrested for her refusal to wear the mandatory hijab.

That post prompted outrage in Iran, including state-affiliated media Tasnim calling for the United States to be removed from the World Cup.

Tyler Adams, who was corrected on his pronunciation of "Iran", said the USMNT "support Iran's people and Iran's team" but are "laser-focused on this match".

Berhalter expanded more on the topic, replying initially: "We had no idea about what US Soccer put out, the staff, the players had no idea. Our focus is on this match.

"I don't want to sound aloof or not caring in saying that, but the guys have worked really hard for the past four years.

"We have 72 hours between England and Iran, and we really are just focused on how to get past Iran and go to the knockout stage of this tournament.

"Of course our thoughts are with the Iranian people, the whole country, the whole team, everyone, but our focus is on this match."

When Berhalter was asked again about the Twitter post, he said: "I can only reiterate that the players and the staff knew nothing about what was being posted. Sometimes things are out of our control.

"We believe it'll be a match where the result depends on who puts more effort on, who executes better on the field, not what happens outside.

"We can only apologise on behalf of the players and the staff. It's not something we're a part of."

Former USMNT coach Jurgen Klinsmann had not helped matters when he accused Iran of having "worked the referee" against Wales, suggesting getting to the match officials and pushing the boundaries of acceptability was "part of their culture".

Iran boss Carlos Queiroz responded in a series of Twitter posts, calling for Klinsmann to be sacked from a role with FIFA, but he would not answer questions on the matter at his own news conference.

Berhalter added little, saying: "I'm up here to discuss the game USA-Iran, not Jurgen Klinsmann.

"You're talking about a guy who's up on the TV. If you want a comment on what he said and how he said it, you should ask Jurgen."

But it was not only questions from Iranian reporters that caused Berhalter some discomfort, with US media relaying Eric Wynalda's claim the coach had asked Gio Reyna to lie about an injury to explain his absence from the USMNT's first match.

"Speaking of a four-year journey, there's been also four years of interacting with you guys," Berhalter said. "I'll leave it to you to decide if I asked Gio to lie about it.

"That's just not who I am, that's not what I represent. If you have to take Eric's word or my word or whatever, feel free. I know what happened. That's not what I represent.

"Like every other person, Gio's a member of this team we care deeply for, and we know he can help the team. It's a matter of when he can help us and how he can help us."