LOS ANGELES : A heavily changed United States lost 3-2 to Turkey on Thursday in an action-packed dead-rubber clash that coach Mauricio Pochettino vowed would not derail the World Cup co-hosts' considerable momentum.

Already crowned Group D winners, the US had arrived in Los Angeles seeking to extend a perfect start with a third win, but with more than an eye on next Wednesday's last-32 meeting against Bosnia-Herzegovina.

For Turkey, already eliminated and without even a goal after disastrous losses to Paraguay and Australia, the only objective was to restore some pride.

Having gone ahead early and then clawed back an equalizer after two Turkey goals, the US fell to a Kaan Ayhan winner deep in stoppage time.

"We had other priorities. We did want to win, we wanted the victory, but there were other things that we need to balance out, and I made the very best decisions," said Pochettino, who made nine changes to his lineup ahead of the Bosnia clash.

"What does it mean to win three (group) matches if you're going to be losing the next one, and you're not going to be winning the World Cup?" he asked a notably tense and spiky press conference after the game.

For the third game running the US had got off to a dream start. Backup center-half Auston Trusty scored unmarked at the far post from a corner.

It was the Celtic defender's first international goal, and -- at just under three minutes -- the second-fastest by the US at a World Cup.

But Turkey did not surrender. Having not scored in 62 efforts across their first two games, it was 63rd time lucky for the Turks, and their star man Arda Guler.

The Real Madrid forward duped Mark McKenzie with a clever dummy, allowing the ball to run down the right flank to Baris Alper Yilmaz.

Yilmaz crossed it back into Guler, who smashed it past Matt Turner to equalize in the 10th minute.

With Brad Pitt and Edward Norton among the Hollywood crowd, the game threatened to become a fight club, as Turkey's bench rushed the field to protest a foul by the combative Sebastian Berhalter, who earned a yellow.

The Americans thought they had restored the lead, McKenzie the second US center-back to put the ball in the net, but the goal was ruled offside.

In the 31st minute the US found themselves behind for the first time this World Cup.

Guler spotted Eren Elmali's overlapping run, feeding it to the wing-back who cut the ball back from the left byline to Yilmaz, who steered it beyond the keeper.

- 'Captain America' returns -

The half-time break proved the perfect tonic for the US. In the 49th minute they were back level from a long throw by McKenzie.

The ball was cleared by Turkey only as far as Berhalter, who did well to smash his shot low into the bottom corner.

The crowd erupted again just before the hour mark as Pochettino sent on Christian Pulisic, undoubtedly US soccer's biggest star.

Nicknamed "Captain America", Pulisic earned his own round of "USA" chants, having not appeared since aggravating an injury against Paraguay two weeks ago.

Pulisic immediately looked lively, twice having efforts blocked from close range after darting runs from the left. He knew less about a ball that looped off his shin onto the post.

Turkey began to knock on the door again. Deep into stoppage time, Ayhan spoiled the US party, slamming the ball home from close range.

Turkey were jubilant, while the American players clustered in a circle after the final whistle, determined to not let the gut punch spoil a campaign that had been off to a flying start.

"If we (had won) the game, is it going to change my mood, my momentum? No. Winning this game, or not winning this game, it's not going to change," said Pochettino.