The Americans had only a handful of seconds left to run out the clock and advance a step closer to the Olympics. With the pressure building with each tick, victory slipped away.

Right off their hands.

The United States, known for producing top goalkeepers such as Brad Friedel, Kasey Keller and Tim Howard, found themselves done in Monday night when substitute Sean Johnson couldn't handle a long shot from Jaime Alas of El Salvador in stoppage time.

The ball bounced off his hands, up over him and into the net, and El Salvador ousted the United States from Olympic qualifying with a 3-3 tie.

"This is probably the worst feeling I've ever felt in my life so far as a pro athlete," U.S. captain Freddy Adu said. "This is going to be hard to get over. But at the end of the day things like this happen. For me, I never want to feel this way again, and I'm going to do whatever it takes to never feel this way again."

The Americans had to win to reach Saturday's semifinals in Kansas City, Kan., and they led 3-2 on Joe Corona's goal in the 68th minute. Officials added 4 minutes of stoppage time onto the game, and U.S. coach Caleb Porter said they were "seconds away" from closing out the win and taking the top spot in Group A. A television clock showed the ball going in 4 minutes, 14 seconds into stoppage time.

What happened is something U.S. midfielder Mix Diskerud said no one wants to experience in life, something he couldn't believe.

"The last 20 minutes after our third goal, all those minutes felt like very, very long hours. But I thought we were going to make it. Everybody thought we were going to make it.," Diskerud said.

"One shot."

Alas stunned the Americans, who missed the Olympics for the second time since 1976 and second time in three Games.

Several Americans dropped to the field in exhaustion and disbelief after the score, and Porter had to try to rally them back to their feet for one last gasp chance that didn't materialize. Porter said he hugged Johnson after the game. The 6-foot-4 keeper did not speak with reporters.

"He feels like he's let everybody down, let his teammates down, and I told him he didn't," Porter said.

El Salvador reached the semifinals, putting it a win away from its first Olympic berth since 1968. Canada, which tied Cuba 1-1 earlier, finished second. Lester Blanco and Andres Flores also scored for El Salvador, a team coach Mauricio Alfaro pointed out had less than two weeks to prepare for this tournament and didn't have the whole roster together until late.

"It was just incredible," Alfaro said of the win through an interpreter.

But Alfaro also said he had told his players to shoot more in the second half to try to pressure Johnson and the El Salvadoran coach said he did feel Johnson made a mistake on Alas' kick.

"The shot didn't have much power," Alfaro said through the interpreter.

Terrence Boyd scored twice for the U.S., and Johnson replaced keeper Bill Hamid in the 39th minute.

After a 2-0 loss to Canada in the second of this three-game, round-robin tournament, the Americans needed to win to advance.

So did El Salvador, and the crowd of 7,889 was about evenly split between the countries keeping the U.S. from a true home-field advantage at LP Field, home of the NFL's Tennessee Titans. El Salvador survived a physical game with plenty of yellow cards on each side.

Boyd went to the sideline with blood on the front of his shirt late in the game. Diskerud said both he and Adu were bitten and showed reporters marks as proof.

"Part of the game, I guess," Diskerud said.

The U.S. had a little bit of time left to try and go ahead but couldn't get anything going before the game ended. The result leaves the Americans adding 2012 to 2004 and 1976 as years they failed to qualify for the Olympics, missing out on a 15th appearance overall.

Boyd got his first start in this round-robin tournament with Juan Agudelo recovering from surgery in New York to fix torn cartilage in his left knee, and Boyd gave the Americans the scoring boost they missed against Canada on Saturday night. The Americans attacked from the start, Boyd scored 61 seconds into the game. Brek Shea dribbled out of three defenders and sent a cross over to Boyd who scored off a left-footed volley.