American fighters Claressa Shields and Marlen Esparza won quarterfinal bouts Monday, guaranteeing themselves a medal in the debut of women's boxing at the Olympics.
This is the first time the sport has been part of the games' program, and both boxers received byes into the quarterfinals.
Shields moved into the semifinals of the middleweight draw with an 18-14 victory against Sweden's Anna Laurell. She will face Kazakhstan's Marina Volnova, who upended top-seeded Savannah Marshall of Great Britain, for the chance to move on to the gold medal fight.
China's Li Jinzi and Russia's Nadezda Torlopova, the second seed, won the other middleweight quarterfinals Monday.
Esparza moved on in the flyweight draw with a 24-16 defeat of Venezuela's Karlha Magliocco. Her semifinal opponent is top-seeded Ren Cancan of China.
The other flyweight semifinal will feature second-seeded Nicola Adams of Great Britain and India's Chungneijang Mery Kom Hmangte.
In lightweight action, top-seeded Katie Taylor got through to the semis thanks to a 26-15 win against Great Britain's Natasha Jonas. The Irish Taylor is a four-time world champion, and will next fight Tajikistan's Mavzuna Chorieva.
Russia's Sofya Ochigava, the No. 2 seed, moved to the semifinals to face Brazilian Adriana Araujo.
All the semifinals in the women's weight classes take place Wednesday.