The United States beat Canada 3-1 on penalties after their CONCACAF women's Gold Cup semi-final ended 2-2 after extra-time, to reach the final of the CONCACAF women's Gold Cup where they will face Brazil.

USA goalkeeper Alyssa Naeher went from villain to hero in minutes after giving away a penalty in the last minute of extra-time but then saving three spot kicks in the shoot-out.

The dramatic finale came at the end of a game which had been played in farcical conditions for the opening 45 minutes.

Brazil comfortably beat Mexico 3-0 in the earlier semi-final in San Diego before a torrential downpour brought the USA-Canada clash into doubt.

There were large patches of standing water across the field at Snapdragon Stadium and once the game got underway it was almost impossible to play normal football on the surface.

With the ball stopping in the water and players sliding around, Mexican referee Katia Garcia went to the sideline for discussions with officials but the game continued in monsoon-like conditions.

USA captain Lindsey Horan and her Canadian counterpart Jessie Fleming both spoke to the referee and appeared to argue for the game to stop.

"It was a little bit of frustration, it's not a day that you can play football and it's really unfortunate. But at the end of the day, me and Jesse were like, 'OK well we have got to move forward and play," said Horan.

Inevitably when the opening goal came, the conditions had a major influence on it -- Vanessa Gilles' ill-advised back-pass stopped dead in a puddle and Jaedyn Shaw pounced on it and slotted home.

At half-time ground staff did their best to push the water off the field but there was a delay to the start of the second half with the rain having caused problems with the referees communication equipment.

As the half progressed, the surface did improve but the quality of the game did not with the USA continuing to play route one direct football.

Canada had a big appeal for a penalty turned down after Fleming went down under challenge from Tierna Davidson.

But eight minutes from the end of normal time, Canada drew level thanks to a powerful header from Jordyn Huitema who rose superbly to angle home a cross from Ashley Lawrence.

The game went into extra-time and the USA got themselves in front with Rose Lavelle's glancing header falling into the path of Sophia Smith who confidently slotted home.

With almost the final kick, Canada lumped the ball into the box and Naeher's attempted punch clear turned into a punch into the head of Gilles and after a VAR review a penalty was given.

A trembling Adriana Leon kept her nerves in check enough to slot home the penalty and take the game to a shoot-out.

But then it was all about Naeher who saved three of the Canadian spot-kicks and scored one herself before wild celebrations at the end of a long and wet night.

The USA had been eliminated on penalties to Sweden in the round of 16 at the World Cup and had lost to Mexico in their final group stage game last week but Horan said their win had shown their spirit was intact.

"That was back to the US mentaltiy that we have talked about and we needed and it is in us. That was not a game where you are going to play football. I don't think there's more than a few completed passes on the ground. But yeah, the grit," she said.

Brazil proved too much for Mexico as they cruised into the final in the earlier semi-final.

The eight-times women's Copa America champion went ahead in the 21st minute when Mexico goalkeeper Stephany Barrera made a mess of a cross from Rafaelle and Adriana reacted sharply to turn in the loose ball.

Eight minutes later, an already difficult task got even tougher when defender Nicolette Hernandez was sent off for denial of a goalscoring opportunity.

Bia Zaneratto was breaking goalwards when Hernandez slid in on the edge of the box and although there was initially no foul awarded, a VAR review led to a straight red for Hernandez.

Mexico's players were in disbelief at the decision and four minutes later their night got worse when Antonia collected a clearance on the edge of the box, cut inside and then buried a perfect left-foot shot into the far corner.

The contest was over three minutes into the second half when substitute Gabi Portilho fired in a low cross which was superbly turned in with a back-heeled flick from Yasmim.