Mexico stunned the United States with only their second-ever victory over the four-time world champions on Monday in the CONCACAF women's Gold Cup.

Lizbeth Ovalle fired Mexico into the lead on 38 minutes, pouncing on a blunder by veteran US defender Becky Sauerbrunn before lifting a cool finish over goalkeeper Alyssa Naeher at Dignity Health Sports Park in Carson, California.

Substitute Mayra Pelayo-Bernal put the seal on the victory for Mexico with a superb individual goal two minutes into stoppage time, curling a long-range effort beyond Naeher to make it 2-0.

The win was only the second victory for Mexico against the US women in 43 games since the teams first met in 1991. The Americans had won 40, with one draw and a lone defeat in 2010.

Ovalle's well-taken opener was also the first time that the US have conceded a goal against CONCACAF opposition in 33 games.

Mexico's win means El-Tri will finish top of Group A in the 12-team tournament, with the US women advancing to this weekend's quarter-finals as runners-up.

"I am proud of my players. They came out with daring, courage and enthusiasm to play a great game against a power like the United States," Mexico coach Pedro Lopez said.

The Spaniard challenged his players to build on the victory for the remainder of the tournament as they head into the quarter-finals.

"I hope that this result is not something sporadic for Mexico but that we can repeat it," Lopez said.

"This win won't mean anything if we don't advance to the semi-finals."

The result was another jolt to the confidence of the US women as they attempt to rebuild in the wake of their earliest World Cup exit last year, to Sweden in the last 16.

"We just didn't play nearly our best," veteran US striker Alex Morgan said afterwards.

"I think we found some pockets here and there, but not nearly enough.

"We didn't execute on the chances we had. I don't think we tested their goalkeeper, I think we got broken down way too easily and Mexico came to play today -- they played really well.

"We're going to have to digest and break down this game. We have to turn it around, pick our heads back up and know that this wasn't nearly our best," said Morgan.

"It's unacceptable," said US midfielder Sam Coffey.

"There's no excuse we can make other than to put our hand up and be accountable and take every single thing that we can from this and make sure that it never happens again," said Coffey.

"That's the DNA of this team -- to learn from our failures.

But it shouldn't happen in the first place. We have to look ourselves in the mirror and move forward."