United States coach Gregg Berhalter slammed the "inexcusable" sending off of defender Sergino Dest on Monday after his team stumbled to a 2-1 defeat against Trinidad & Tobago in the CONCACAF Nations League.

Despite the loss, the US advanced to the semi-finals of the Nations League -- and sealed their place in next year's Copa America -- with a 4-2 aggregate quarter-final victory.

But what should have been a routine second leg in Port of Spain was made harder than it needed to be after Dest's dismissal towards the end of the first half.

The US at the time were leading 1-0 after Antonee Robinson's 25th-minute header and appeared to be cruising into the last four.

But the match was turned on its head in the 39th minute after a moment of madness from Dest.

The US defender was booked by referee Walter Lopez after kicking the ball away petulantly, and then picked up a second yellow card after continuing to harangue the Guatemalan official.

Trinidad subsequently equalised through Reon Moore on 43 minutes and then scored a winner through Alvin Jones' free-kick on 57 minutes.

Although Trinidad never looked like scoring the five goals they required to win on aggregate, Berhalter could not hide his fury at Dest's self-inflicted red card after the game.

"He put a number of guys in jeopardy, made a number of guys do a lot of extra work in this weather, and it's inexcusable," Berhalter said of Dest.

"We pride ourselves in staying mentally disciplined, battling through any type of conditions, whether they're good decisions or bad decisions. We're supposed to keep going and respond in an appropriate way, and that obviously wasn't the right response from Sergino."

Dest, who had been lambasted by team-mates Tim Ream and Matt Turner as he trudged off following his red card, issued an apology on Instagram after the game.

"I want to apologize to my team-mates, staff and fans and whole nation for my behavior; it was unacceptable, selfish, and immature," Dest wrote on Instagram.

"I let my team down. It's something I have to learn from and it won't happen again."

US goalscorer Robinson described Dest's dismissal as a "moment of unprofessionalism."

"Disappointed we didn't get the win," Robinson said. "We started the game pretty well and had things under control and then a moment of unprofessionalism kind of went against us.

"But we'll take it," he added. "We're in the semi-finals of the Nations League and we're in the Copa America, so it's still been a successful break."