Great Britain are one win from a first Davis Cup title in 79 years following Andy and Jamie Murray's doubles victory against Belgium.
The Scottish brothers beat Steve Darcis and David Goffin 6-4 4-6 6-3 6-2 to put the visitors 2-1 up in Ghent.
Britain require one win from Sunday's reverse singles matches to secure their first Davis Cup victory since 1936.
Andy Murray will play Goffin, with Kyle Edmund scheduled to face Ruben Bemelmans in the final match.
Captains can change their nominations up until one hour before the 12:00 GMT start on Sunday, and Britain's Leon Smith could bring in James Ward for Edmund if it comes down to a fifth rubber.