Johanna Konta and Heather Watson were victorious again as Great Britain defeated Estonia 3-0 to progress through to a Fed Cup play-off against Hungary on Saturday.
Konta and Watson both won their singles matches as Britain saw off Portugal 3-0 on Wednesday, and the pair were triumphant again on Friday against host nation Estonia in Tallinn.
After Watson had thrashed 15-year-old Katriin Saar 6-1 6-1 in just 57 minutes, Konta eventually emerged victorious in a much-tougher encounter with world number 27 Anett Kontaveit to earn Britain an unassailable 2-0 lead in the tie.
Anna Smith and Katie Boulter then wrapped up another whitewash win when they swept aside Elena Malygina and Saara Orav 6-1 6-1 in the doubles.
Konta served twice for the first set against Kontaveit but ended up losing it on a tie-break as Estonia, who also beat Portugal in their opening match, drew first blood.
However, world number 11 Konta hit back and eventually clinched a 6-7 (5/7) 6-4 6-2 victory to send Britain through to showdown with Group C winners Hungary.
Konta said on British Tennis' official Twitter account: "I knew going into the match that she can play at a great level and I really just had to trust in myself that I was going to be able to maintain the level for longer than she could, and I managed to do that in the end so really happy with myself.
"However, there was very little in it. She kept on raising her level and made it incredibly tough for me."
Konta added: "Really happy to have given us the 2-0 and given us the chance to play for a World Group II play-off tomorrow.
"Every match is a battle but I'm really enjoying being with the team and really enjoying fighting here."
If Anne Keothavong's team beat Hungary they will qualify for the World Group II play-offs in April.
Britain have made it to the World Group II play-offs three times in the last six years - including last year against Romania - but were beaten on each occasion.
Britain have not played in the Fed Cup World Group since 1993.