The USA and pre-tournament favourites Canada stayed on track to meet in the Olympic men's ice hockey final with quarterfinal overtime wins on Wednesday.
Mitch Marner scored in overtime as Canada saw off the Czech Republic 4-3 to reach the semifinals.
The Americans were also made to fight till the end against Sweden before Quinn Hughes netted 3min 27 sec into overtime for a 2-1 victory in front of thousands of US supporters in Milan's Santagiulia Arena.
Canada go on to face reigning champions Finland and the USA will play Slovakia, with both semifinals on Friday.
Canada had cruised through the preliminary round and defeated the Czechs 5–0 just six days previously. But the 2024 world champions proved far tougher opponents this time until Marner applied the decisive touch.
"(It was) adrenaline: trust in your skill that you work on so hard," Marner said.
"You just trust yourself to make a play there, and I was lucky enough to score."
Macklin Celebrini put Canada ahead within four minutes, before Lukas Sedlak levelled four minutes later.
The Czech Republic pulled ahead thanks to David Pastrnak's first goal of the tournament after a quarter of an hour.
The Canadians raised their game in the second period, outshooting their opponents 17 to 5. But they lacked precision in the final touch and only a blatant foul by Michal Kempny opened up the space for Nathan MacKinnon to make it 2–2.
CROSBY BLOW
Canada lost captain Sidney Crosby, a two-time Olympic champion in 2010 and 2014, with a leg injury that ruled him out for the rest of the game.
The Czechs regained the lead with a blistering counter finished off by Ondrej Palat.
The Canadian reply came with a long-range shot from Nick Suzuki before Marner delivered the winner.
The USA seized the iniative in their game with a second period goal from Dylan Larkin but Mika Zibanejad made it a fight for the Americans when he brought Sweden level in the third.
Deep in overtime, Hughes skated in front of the Swedish goal and fired past the Swedish goaltender as the US bench and a large per centage of the crowd erupted in celebrations.
Both Canada and the USA have rosters packed with players from the National Hockey League, who are competing at an Olympics for the first time since 2014.
Earlier, Finland scraped through to the final four by beating Switzerland 3-2 in another contest that went to overtime, while Slovakia thrashed Germany 6-2.
Artturi Lehkonen was the hero for Finland as he scored the overtime winner in the three-on-three extra period.
The Slovaks, bronze medallists four years ago, took charge at the end of the first period with Pavol Regenda scoring after 19 minutes.
The rest of the game was a Slovak demonstration of skill, with Milos Kelemen and Oliver Okuliar scoring two quick-fire goals before Dalibor Dvorsky grabbed a fourth just after half an hour.
The 2020 NHL MVP Leon Draisaitl set up Lukas Reichel to keep Germany's hopes alive after 35 minutes but that was quickly extinguished at the start of the final period by Regenda's second goal.
To round things off, Tomas Tatar responded to Frederik Tiffels's power-play score after 50 minutes with a goal of his own.