Russia is chasing its fourth straight gold medal sweep of the Olympic synchronized swimming events after taking the team lead.
The Russians scored 98.1 points in the technical routine Thursday afternoon to lead China by 1.1 points heading into the free routine on Friday.
Points from both routines will be combined to determine the medal winners.
Spain was 1.9 points back in third place and Canada finished fourth, 3.7 points off the pace.
The United States was represented here by Mary Killman and Mariya Koroleva, who finished 11th in the duets competition. But the U.S. did not qualify a synchronized swimming team for the first time ever at the Olympics.
Russia has swept the sport in the last three games by winning every gold in the team and duets competition since 2000. Russian favorites Natalia Ishchenko and Svetlana Romashina won gold in duets on Tuesday. Silver and bronze went to Spain and China in that order.