"It was like having an argument with my son.
I tried to explain but he just wouldn't listen," said US head coach, Larry Brown, who had asked for a stoppage with 23 seconds to go.
"I called the time out and then saw the clock and tried to cancel it, but (the officials) wouldn't let me. I tried to explain this to (the Spanish coach), that I meant no disrespect."
Stephon Marbury finally found his shooting touch, vital in the fourth quarter, to steer the United States to their victory.
The defending champions and three-times gold medallists, had gone into the game in the unfamiliar role of being underdogs, after losing to both Puerto Rica and Lithuania in the preliminary round. Spain were undefeated.
"Coming into the Olympics I hadn't played all summer so I wasn't in my rhythm. But I have taken some extra shooting practice to get it back," said Marbury.
The Americans put together their best effort of the tournament, with Marbury breaking out of his poor form to score 31 points.
The United States came out aggressively, running up a five point lead in the first minute.
But with Tim Duncan once again in foul trouble, Pau Gasol began to dominate inside, racking up 18 points and six rebounds in the first half alone.
Clinging to a one point lead to start the third quarter, the Americans once again went on an early run to open up an eight point lead, only to see Spain level the score at 63-63 and then take a seven point lead to start the fourth quarter.
But Spain could only get as close as four points in the final frame before Marbury's three pointer closed the door.
"We were there for about 35 minutes. I'm hurt.
That was a big chance for our team to make a statement, to get a lot of respect," said Gasol, who ended with 29 points and six rebounds.
In another match, Lithuania beat China 95-75 on Thursday, spoiling another dominant performance by Yao Ming to advance to the men's Olympic basketball semi-final.
China took a surprise early lead, but Lithuania responded with a 13-point run to take control in the first half on their way to remaining the only unbeaten team at the tournament.
Yao was a force at both ends of the court, scoring 29 points and grabbing 11 rebounds.
Reserve guard Arvydas Macijauskas also had a big game for Lithuania, knocking down 32 points for the bronze medallists at the last three Games.