The U.S.'s future in the World Cup will be decided Tuesday against Iran. After draws against Wales and England, the U.S. can only advance to the knockout stage with a win; anything else and they will be boarding a flight home.

Iran, ranked nine spots lower than USA in the FIFA rankings, defeated Wales and was blown out by England, so they are facing a similar situation as the U.S. -- though a draw could also result in them making it out of the group stage as well. Wales can only advance with an unlikely dominating performance against England.

The match has almost been eclipsed by controversy over the U.S. Soccer Federation posting a photo of the Iranian flag on Twitter without the Islamic symbol. The post was to show support for protesters in Iran, and has earned calls for FIFA to kick the USA out of the competition. That's unlikely, but Iran can handle it on the field by simply beating the USA. FiveThirtyEight's predictions give the U.S. a 38% chance of winning versus 31% for Iran (with a 31% chance of a draw).

This is only the third time the two countries have met. They faced off in another politically heated match in the 1998 World Cup when the U.S. government called Iran the "most active" sponsor of terrorism just weeks beforehand. Iran won that match, 2-1.

The other two games on Tuesday will be in Group A, including the final match for the home country. Unfortunately for local fans, Qatar has already been eliminated from contention for the knockout stages. Netherlands can advance with a win over Qatar (or a draw and some help), while the winner of Ecuador-Senegal will also advance. Ecuador would advance with a draw.

Tuesday's schedule of matches:

• Ecuador vs. Senegal, 10 a.m., FS1
• Netherlands vs. Qatar, 10 a.m., Fox
• Iran vs. United States, 2 p.m., Fox
• Wales vs. England, 2 p.m., FS1

The White House declined to comment on the Iranian flag flap created by the U.S. Soccer Federation's removal of the Islamic emblem from a photo on the U.S. men's national team's Twitter account.

National Security Council spokesperson John Kirby said the White House would not have comment during a White House press briefing Monday afternoon.

"This isn't the kind of thing that you would -- that the White House would -- comment on," Kirby said at the briefing. "USA soccer is a private entity, and they make their own decisions about those kinds of things, and we wouldn't comment on that. We wish them all the best tomorrow."

Kirby also said he wasn't aware of any conversations or consultations involving anyone from the U.S. government about the U.S. Soccer Federation's decision to alter the flag.

The logo was later added back to the flag in the team's Twitter header. The federation had said it was done to support protesters in the country currently demonstrating against the totalitarian regime and its treatment of women.

-ABC News' Sarah Kolinovsky

U.S. national team coach Gregg Berhalter tried to keep the focus on Tuesday's game at a press conference as he faced questions about why the U.S. team's Twitter account removed the Islamic emblem from Iran's flag in a post Sunday. He also insisted his team had no knowledge of the post.

The U.S. soccer federation said it removed the logo to show support for those protesting in the country against authoritarian rule and its treatment of women.

Berhalter tried to keep the focus on the uniting power of sports and the World Cup, even as Iran called for the U.S. to be kicked out of the World Cup for altering its flag.

"Sport is something that should bring people together, bring countries together," Berhalter said. "When you look at the Olympics, to see all those countries competing at the same time, is a wonderful event. The World Cup is very similar, where people come from all around the world. Fans come from all around the world, and you get to compete on the field, as brothers, so sport does have the ability to do that."

U.S. captain Tyler Adams was criticized by an Iranian reporter for mispronouncing "Iran," which he apologized for, and he was questioned about discrimination in the U.S., saying it is everywhere but there has been progress. But he also deflected attention back to the game.

"Listen, we support Iran's people and Iran's team. But that being said, you know, we're laser focused on this match as they are as well," Adams, 23, told reporters. "We know how important this is for our progress of our team and what we want to do to prove to our country, you know, how hard we've been working. And we know they want to do exactly the same."

The U.S. must defeat Iran Tuesday to advance to the knockout stage of the tournament.

-ABC News' Karyn Rhodus

Portugal dispatched Uruguay on Monday, taking its second win of the tournament and guaranteeing superstar Cristiano Ronaldo will see the knockout stage in what is almost certainly the 37-year-old's last World Cup.

Portugal won 2-0 behind two goals from Bruno Fernandes. The Manchester United star -- briefly Ronaldo's teammate before Man U dismissed the star -- scored the match's first goal in the 54th minute and then added the clincher in the 93rd minute on a penalty kick.

Portugal will play South Korea on Friday, but will likely rest some players to get them ready for the knockout stage.