Heather Watson powered Great Britain a 1-0 lead in their final best-of-three Fed Cup match with Turkey in Estonia.
Watson, ranked 72nd in the world, registered a 6-0 6-1 victory over 163rd-ranked Ipek Soylu in one hour and 3 minutes.
Great Britain are top of Group C after successive 3-0 victories over Portugal and Latvia.
Victory will guarantee their place in Saturday's promotion play-offs, where they would face the winners of Pool B.
Unlike the men's team competition, the Davis Cup, which has a World Group of 16 nations, the Fed Cup divides its top teams into two groups of eight - World Group I and World Group II.