D.C. United's emotions in the final few moments of its 1-0 victory over Olimpia of Honduras tonight swayed from anticipation to horror to anger to jubilation to relief.

In an almost inconceivable ending to a CONCACAF Champions Cup quarterfinal at Sam Boyd Stadium, United goalkeeper Tom Presthus redeemed himself for a potentially game-turning foul by stopping a penalty kick by former teammate Arnold Cruz.

As the fallen Presthus squeezed the ball and his ecstatic teammates rushed toward him, referee Carlos Batres checked his watch and then blew the whistle to signal the end of a stirring match.

"I've never seen anything like it -- never," United Coach Thomas Rongen said. "For a game to end on that play, with so much at stake, I just can't believe it. It was a magical moment."

The victory sent defending champion United to Friday night's semifinals against Mexican power Necaxa, which defeated Saprissa of Costa Rica, 3-2, in tonight's second match. United's triumph also kept alive its hopes of winning an eight-team tournament that will send its winner to the inaugural world club championships in Brazil early next year.

Forward Jaime Moreno scored the only goal in the 68th minute, pushing in reserve Carey Talley's cross from the right wing. United then survived a couple of frightening moments and seemed safely on its way to the next round.

But while chasing a loose ball at the edge of the penalty area, Presthus knocked down Olimpia forward Wilmer Velasquez. Batres immediately awarded a penalty kick, which are converted at about a 90 percent rate. Up stepped Cruz, a veteran defender who played for United and the San Jose Clash during the 1997 Major League Soccer season before resuming his career in Central America.

"I just had a feeling that he was really going to try to hammer it [in that direction], just the way he was setting up the ball, his mannerisms," Presthus said. "I was leaning to my right and I was expecting a shot to the right. That was real lucky."

As Cruz prepared to shoot, Rongen was planning what players to choose for the tiebreaker. "No disrespect to Tom," Rongen said, "but that's usually a goal."

On the sideline, reserve goalkeeper Mark Simpson didn't have any doubts. "All of us on the bench knew he would stop it," he said. "We were saying, `He's got this, he's got this.' He was on tonight."

The save ended a frustrating night for United, which had trouble navigating the narrow field -- it's about seven yards narrower than RFK Stadium -- missed some early chances and survived some scares by Velasquez. A few minutes before the penalty kick, Presthus stopped Denilson Costa's shot from a sharp angle, and prior to Moreno's goal, the Olimpia sharpshooter's clear bid from 10 yards skimmed off the top of the crossbar. Moreno had hit the crossbar with a powerful header in the first half and Olimpia goalkeeper Carlos Prono made three superb saves overall.

"We had a chance to win," Velasquez said, "but that's the nature of the game."

United had anticipated a difficult first match, and that is exactly what it got. Olimpia had plowed through the Central American qualifying tournament and boasted a formidable attack that promised to test United's sometimes inconsistent defense.

Finally, Talley, who entered 10 minutes earlier for John Maessner, found some space on the right side and found Moreno charging toward the net. Moreno's touch was solid, and the ball quickly struck Prono's foot before settling into the right corner.

In the second game, Necaxa cruised to a 2-0 halftime lead on goals by Agustin Delgado in the 14th minute and Sergio Vasquez in the 37th. After Steve Bryce scored for Saprissa 13 minutes into the second half, Alex Aguinaga volleyed in Delgado's pretty cross in the 64th minute. Saprissa's Walter Centeno added a goal in the closing moments.

In Friday's other semifinal, MLS's Chicago Fire will play Alajuela of Costa Rica, which on Tuesday upset tournament favorite Toluca of Mexico, 1-0. Chicago advanced with a 2-0 victory over Joe Public of Trinidad and Tobago.

GALAXY 4, RAPIDS 0: Cobi Jones scored in both halves and Steve Jolley added a first-half goal in a Major League Soccer game in Pasadena, Calif.

The victory before a Rose Bowl crowd announced at 10,098 moved the Galaxy (19-11) four points ahead of second-place Colorado (19-10) in the race for the conference lead and home-field advantage in the first two rounds of the playoffs. Los Angeles has two matches remaining, the Rapids three. MLS teams receive three points for regulation victories, one for shootout victories and none for losses.

Goalkeeper Kevin Hartman did not need to make a save as he posted his 10th shutout of the season and 20th of his MLS career, one behind Kansas City's Tony Meola, who holds the four-year-old league's record.

It was the first time in the Rapids' history that the team did not get off a shot on goal.