The US men's basketball team lost for the second time in Athens when European champions Lithuania came from behind in the last quarter to beat them 94-90.
Three successive three-pointers in the last four minutes from guard Sarunas Jasikevicius proved vital for Lithuania
He led all scorers with 28 points, while Richard Jefferson paced America's offensive effort with 20 points.
The loss means the USA must win their last group game against Angola to advance to the quarter-final stage.
"We have to play four quarters of our best basketball, or it's going to be kind of ugly," said US coach Larry Brown.
"I'm disappointed to say the least, but I think we're getting better except for a bit of a meltdown in the fourth quarter."
Jasikevicius said he thought the rest of the world had caught up with the Americans.
"There was an awe when playing the Americans maybe 17 or 18 years ago, but a lot of countries have caught up," he said.
"We beat a great basketball team. Emotionally, it's great, but in theory it doesn't help much. We have to win in the quarter-finals."
He saw side give perhaps their best all-around performance of these Olympics.
However, the Americans missed 11 of 33 shots from the foul line, which proved crucial.
Reigning world champions Serbia and Montenegro lost to Spain to put their chances of progressing in peril.
They must now beat China - who also need a win to stay in the Olympics - in a crunch final group game.
"We're not going to give up on Serbia. Of course we have a chance," said China coach Del Harris.