Andy and Jamie Murray joined forces in the doubles to give Great Britain a 2-1 lead in their Davis Cup first-round tie against Japan in Birmingham.
The Scottish brothers beat Yoshihito Nishioka and Yasutaka Uchiyama 6-3 6-2 6-4 to leave the holders one win from a quarter-final place.
Andy Murray will hope to secure victory when he faces Kei Nishikori on Sunday.
Nishikori, the world number six, was rested for Saturday's doubles after beating Dan Evans on Friday.
Evans, ranked 157th, would line up against world number 87 Taro Daniel if a decisive fifth rubber were required.