SOCHI, Russia -- A 3-2 win over the archrival United States was a big boost to Canada's confidence, but history shows Wednesday's result won't mean much if the two women's hockey powers face off for Olympic gold.

This tournament format introduced at the world championship two years ago has pitted the women's hockey heavyweights against each other in the preliminary round before a second meeting in the final.

Each country has won the round-robin matchup, only to lose the final in both 2012 and 2013.

But after dropping four straight exhibition games to the Americans before their arrival in Sochi, the Canadian women could feel good about themselves heading into a four-day break before Monday's semifinal.

"Losing the last four games, this is a huge boost for our confidence," captain Caroline Ouellette said. "We know we're even with them and if we do the little things right, we have a good chance to win."

It was Canada's first win against the U.S. under head coach Kevin Dineen, who was hired Dec. 18 following the departure of Dan Church. Dineen was behind the bench for three of those four losses.

Canada and the U.S. already had berths in Monday's semifinals locked down before their game. Both countries opened the tournament 2-0 in Group A.

The top four countries in the International Ice Hockey Federation's world rankings were seeded in Group A and fifth through eight in Group B.

The top two countries in Group A head to the semifinals, while the bottom two face the top two from Group B in Saturday's quarter-finals.

Finland will face the loser of Thursday's game between Sweden and host Russia, while Switzerland takes on the winner in the quarter-finals.

Trailing 1-0 after two periods, Meghan Agosta-Marciano of Ruthven, Ont., scored a pair of goals and had an assist for the defending champions on her 27th birthday.

Linemate Hayley Wickenheiser of Shaunavon, Sask., who was Canada's flag-bearer in the opening ceremonies, scored a controversial goal and assisted on Agosta-Marciano's equalizer.

Charline Labonte of Boisbriand, Que., stopped 25 of 27 shots for the win and stoned Kelli Stack on a short-handed breakaway in the second period. Jesse Vetter stopped 28 of 31 in net for the U.S.

Dineen's choice to put Labonte in goal was intriguing because Shannon Szabados has started in all world championship finals for Canada since her shutout of the Americans in the 2010 Olympic final.

Hilary Knight scored a power-play goal for the U.S. in the second period with defenceman Anne Schleper pulling them within a goal with 65 seconds remaining.

With Vetter pulled for an extra attacker, Canada was dinged for too many men with 30 seconds left and killed the penalty two players down until the buzzer.

The U.S. women possess more individual speed than Canada, but they're shorter on players with a history of high-pressure game experience.

Wickenheiser and Jayna Hefford are playing in their fifth Olympic hockey tournament, Ouellette her fourth and Agosta-Marciano her third.

"Our team has experience and composure that when the chips are down, we know how to win," Wickenheiser said. "We have enough players who have been there before."

After assisting on Agosta's power-play goal with a cross-ice pass at 2:21 of the third, Wickenheiser whipped the puck from close range into Vetter's pads.

The puck squirted behind Vetter and crossed the goal-line, although when the officials blew the whistle was in dispute. Upon review, Finnish referee Anna Eskola awarded the go-ahead goal to Canada at 3:54.

"I did hear the whistle blow before the puck went in," U.S. coach Katey Stone said. "We had a lot of time left in the game at that point so I'm not going to hang my hat on that one. I think we can play better."

Dineen bluntly stated after Monday's 3-0 win over Finland that Agosta-Marciano had played "pretty stinky" until she scored in the third period.

The forward is one of Canada's fastest skaters with a gifted pair of hands. Agosta-Marciano was an impact player throughout Wednesday's game despite fighting a cold.

"I've been a little bit under the weather, but I'm not going to let that get to me," Agosta-Marciano said. "I'm going to keep battling. Hockey players, they all have bad games sometimes. I'm not going to let it bother me."

Said Wickenheiser: "She's a goal scorer and if she's not scoring, she's pretty pissed off. When she scores, she's feeling good and that's a great place to have her."

Agosta-Marciano collected a hat trick on her 19th birthday at the 2006 Winter Games in Turin, Italy. She's Canada's hat-trick leader at the Olympics with three in total. She was one short of a fourth Wednesday.

"This is my third Olympics, I've always had my birthday here and it is special," she said. "It's even more special to be able to represent your country."