Serena Williams made it a hat-trick of victories over fellow Americans to move into the fourth round of the US Open.
The world number one had a much tougher time of it against Varvara Lepchenko than she had against either Taylor Townsend or Vania King but was ultimately a convincing 6-3 6-3 winner in breezy conditions.
Lepchenko, who is of Uzbek descent, had not won more than two games in a set against Williams in their two previous meetings.
She was also looking to become only the second left-handed player after Ekaterina Makarova to beat Williams at a grand slam.
The world number one has shown tunnel vision so far this tournament after her slam wobbles this season and quickly moved into a 3-1 lead.
Lepchenko fought back to level with some terrific play but could not prevent Williams pulling away to take the opening set.
The second was a real battle but Williams won the points that mattered, holding off break points in the fifth game and then forging ahead for 4-3.
That proved the crucial stage of the match and Williams clinched victory after an hour and 35 minutes when Lepchenko netted a backhand.
The two-time defending champion next plays Estonian Kaia Kanepi, who upset 15th seed Carla Suarez Navarro 7-5 6-0.