Written off after their opener and branded failures back home, Stephon Marbury and the Americans are showing signs that they just might be the team to beat after all.

For a change, the face of frustration belonged to someone other than an American after Marbury’s performance. He set a U.S. men’s Olympic record with 31 points and broke the team mark with six 3-pointers, leading the suddenly accurate Americans into the semifinals with a 102-94 victory over Spain yesterday.

In a game that ended with the opposing coaches swearing and pointing at one another, the United States finally started hitting jump shots — just as Larry Brown predicted.

“They were very good on 3s. That was something new in this tournament,” Spain’s Pau Gasol said. “They looked motivated, and it’ll be hard to beat them if they keep playing like that.”

After spending 90 minutes practicing jumpers in an empty gym on a day off, Marbury made half of his team’s 12 3-pointers and was a big reason why the previously undefeated Spaniards are now out of medal contention.

As the teams left the court, Spanish coach Mario Pesquera and Brown had to be separated by their assistants in an argument over a timeout Brown took with 23 seconds left and his team up by 11 points.

“I had — and I stress the word ‘had’ — a lot of respect for Larry Brown,” said Pesquera, who smirked and shook his head when he heard Brown explain that he tried to rescind the timeout. “Dean Smith would have never done anything like that.”

Marbury scored just 21 points in his team’s first five games, missing 24 of 30 shots. The Americans lost two of them, to Puerto Rico and Lithuania.

But those struggles are in the past, and the Americans now have a chance to win the gold medal. Next up is a semifinal today against the winner of the Greece-Argentina game. The other semifinal pitted Lithuania, which defeated China 95-75, against Italy or Puerto Rico.

Marbury’s six 3s broke the record of five set by Reggie Miller against China in 1996, and his scoring total passed the mark of 30 points shared by Charles Barkley (1992 vs. Brazil) and Adrian Dantley (1976 vs. Yugoslavia). The Olympic record is 55 points by Oscar Schmidt of Brazil against Spain in 1988. The record for any U.S. player is 35 by Lisa Leslie against Japan in 1996.

Allen Iverson added 16 points, making three 3-pointers, and the Americans finally resembled U.S. teams from the past three Olympics. They didn’t get rattled by a large disparity in fouls (27-18), they knocked down their free throws to maintain the lead in the final two minutes, and they topped 100 points for the first time in the tournament.

The Americans finished 12-for-22 on 3-pointers after shooting a tournament-low 24 percent in their first five games.

“We’ve been playing against so much zone, it doesn’t really matter anymore,” Marbury said. “We’re starting to like playing against zones.”

Marbury had struggled the most in the team’s first five games, uncomfortable with Brown’s insistence that a point guard should run the offense rather than score. Historically a shoot-first, pass-second player, Marbury’s mind-set was fundamentally at odds with his coach’s.

“Playing under coach Brown is not easy,” Marbury said. “It’s tough because he demands so much from you — to try to play your game and try to do what he wants, and have that all combine in one has been a challenge to me. But it’s been a great challenge.”

Gasol led Spain with 29 points but was held to just four in the fourth quarter by a tenacious American defensive effort, which quieted a crowd of 14,500 that included Spain’s King Juan Carlos.

“It was said that the public supports the weaker team. I think in this case the public was solidly behind the stronger team because we were the stronger team,” said Pesquera, who also complained that the officials allowed the Americans to get away with traveling violations.

“I think this game was played under NBA rules, not FIBA rules,” he said.

Several Spanish players threw their hands up and stared at the American bench in disgust when Brown called his late timeout. Pesquera wasn’t buying Brown’s explanation.

“I tried to apologize, I tried to explain, and he kept saying something about the NBA. I would never try to embarrass anybody,” Brown said. “Hopefully I’ll learn to handle these situations, which are new to me, a little bit better.”

Tim Duncan scored the Americans’ first five points and blocked Spain’s first shot, but he was on the bench just 4 1/2 minutes into the first quarter and stayed there for the rest of the half after picking up two fouls.

In a seesaw second quarter, the Americans went ahead by eight points, feeding off the defensive energy of Dwyane Wade, before Spain rallied with an 11-0 run.

A 7-0 run by Spain tied the game late in the third quarter, but Carmelo Anthony ended the period with a 3 to put the Americans up 74-67. Marbury’s last 3-pointer provided a seven-point cushion with 3:45 left, and Gasol didn’t score his first points of the fourth quarter until 2:02 remained.

“I’m not exhausted, I’m hurt because that was a big chance for our team to make a statement,” said Gasol, who played all 40 minutes. “We deserved better. We’re out, and it hurts to say that.”