The United States looked poised to lock up a spot in the knockout round with second-half goals from Jermaine Jones and Clint Dempsey. But Portugal's late goal will force the Americans to wait until Thursday to ensure their place in the Round of 16.
Nani opened the scoring in the fifth minute as the Portugal winger capitalized on a Geoff Cameron defensive error to put the United States in an early hole. Nani's goal was the sixth by a Manchester United player this World Cup. Only Bayern Munich players (nine) have scored more.
The United States has conceded seven goals in the first five minutes of World Cup games, the most by any team in World Cup history.
But the Americans answered with an offensive surge of their own. By the 30th minute, the United States had already recorded as many shots (eight) as it did in the entire game against Ghana.
Michael Bradley in particular picked up his play in the second game. Bradley completed 35 passes in the first half, as many as he did across 90 minutes against Ghana.
Nearly 20 minutes into the second half, Jermaine Jones put the United States on the board with his first goal in his past 27 international games.
Jones' goal, which was the 2,300th in World Cup history, was measured at 28.4 yards.
That's the longest open-play goal for the United States at the World Cup in the past 50 years.
Jones' goal was the third by the United States outside the box since 1950, joining Dempsey (2010 vs. England) and Eric Wynalda (1994 vs. Switzerland).
Dempsey gave the United States what appeared to be the game-winner in the 81st minute, his fourth career World Cup goal. Dempsey is tied with Bert Patenaude for the second-most World Cup goals in United States history -- Landon Donovan hold the record with five.
Portugal answered late on a superb Cristiano Ronaldo cross to Varela, who buried the equalizer to earn a crucial point.
Varela's goal was officially timed at 90' +4:33, making it the latest recorded World Cup goal in a regulation game.
Ronaldo's assist was his only completed cross in the game, still more than the entire American squad (0-from-14).
Portugal dropped points when scoring first for the first time in its World Cup history (previously 11-0-0). On the other hand, the United States still has never won in the World Cup, falling to 0-16-5 when conceding the opening goal.
The Americans will advance with a win or a draw against Germany on Thursday. The United States could also advance with a loss if Portugal or Ghana do not surpass them on goal differential.
According to ESPN's Soccer Power Index, the United States have a 76 percent chance to advance to the knockout round, up from 64 percent prior to the game against Portugal.
The Germans enter Thursday's game against the United States in familiar territory. There have already been questions about how much attacking will occur in that game, as there's precedent for German involvement in a mutually assured advancement situation.
In 1982, West Germany was in a group with Algeria, Austria and Chile. A 3-2 Algeria win in its last game meant Algeria would be the first African team to reach the knockout stage unless West Germany beat Austria by one or two goals -- in which case both European sides would advance.
After Germany's Horst Hrubesch put the Germans in front in the 10th minute, both teams realized they were through if results held and basically stopped playing for the final 80 minutes (zero shots, barely any tackles, etc.).
The incident is what prompted FIFA to change the format of the final game of the group stage. All four teams in a group now play their third game simultaneously to avoid this scenario.