The second set of matches of the day are underway in Qatar with the U.S. men's national team facing a must-win against Iran.

The U.S. can only advance to the knockout stage with a victory after draws against Wales and England. If they lose, the U.S. team heads home.

For Iran, who defeated Wales but was dominated by England, a win or a draw can move the team to the knockout round.

In the other match, between England and Wales, Wales can only advance with a win against England, a draw from U.S.-Iran and a lot of help in goal differential. England is likely to advance as it stands as the top team in Group B and could advance even if it ties with Wales.

The first two teams to advance out of group play are Senegal and Netherlands. Netherlands cruised to a 2-0 victory over host country Qatar, while Senegal earned a 2-1 victory in a must-win match.

Senegal led 1-0 at the half on a penalty kick goal from Ismaila Sarr in the 44th minute. But Ecuador tied the game 1-1 in the 67th minute on a goal by Moises Caicedo off a corner kick. A draw would've meant Ecuador advanced to the knockout round.

But Senegal's Kalidou Koulibaly scored the go-ahead goal just three minutes later off a free kick. The goal stood up as the game-winner.

A heavily favored Dutch side had no issues with Qatar, which had already been eliminated from contention for the second round. Cody Gakpo scored in the 26th minute and Frenkie de Jong added a second goal just four minutes into the second half. Netherlands finished atop the group with the win.

Netherlands will play the second-place team in Group B in the next round, while Senegal will face the winner of Group A. The U.S., if they advance over Iran, will likely take on Netherlands.

Senegal and the Netherlands hold one-goal leads at the half in the final matches in Group A.

Senegal, which likely needs a win to advance, scored a goal on a penalty kick by Ismaila Sarr in the 44th minute. Senegal leads Ecuador, 1-0. Ecuador needs a win or draw to advance to the knockout stage.

The Netherlands has had no problems with the host country of Qatar in the first half, leading 1-0 behind a goal from Cody Gakpo in the 26th minute. A win would put the Dutch into the second round.

The first two matches of the day are underway in Qatar, including the final game for the home squad.

Qatar, which cannot advance to the next round after losses in its first two matches, faces the Netherlands, which currently stands atop Group A. The Netherlands would advance with a win.

In the second match, Ecuador and Senegal face off with the winner guaranteeing a spot in the knockout stage. A draw would also be enough for Ecuador to move on.

If Senegal-Ecuador tie and Netherlands loses, it will come down to goal differential to determine whether Netherlands or Senegal advances. Netherlands is currently plus-2 in goal differential on Senegal, so they are looking good.

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