The U.S., who gave Klinsmann his first win as coach with a 1-0 victory over Honduras at the weekend, slumped to their third loss in five games under the German's attack-minded direction after Jaime Ayovi headed in a cross from team mate Walter Ayovi in the 79th minute.
Klinsmann pledged to turn the U.S. into a more offence-driven side after taking over from Bob Bradley in July, but the transition is yet to show on the scoreboard, with only two goals produced from the last five games.
"In the first half we controlled the match completely," Klinsmann told reporters. "In the second half it opened up because we made a lot of changes - it was our second game in three days.
"A team like Ecuador was a good benchmark. If you make one little mistake they punish you, and that's what they did."
It was Ayovi's second goal in as many matches after he scored in Ecuador's 2-0 win over Venezuela on Friday.
The Americans were without playmaker Landon Donovan, who was sidelined with a quadriceps injury. Like Klinsmann, the veteran international also came away optimistic about the new-look U.S. side's prospects.
"I thought we played pretty well for long stretches, just like in the Honduras match," Donovan said. "So many of these games come down to one play, and that's what you saw."
