Storm Sanders and Ajla Tomljanovic won their respective singles rubbers on Thursday to help Australia beat Belarus and book the team's spot in the semi-finals of the new-look Billie Jean King Cup finals.

Australia, chasing an eighth title in the women's team competition which was previously called the Fed Cup, had defeated Belgium in its opening Group B tie and its unassailable 2-0 lead against Belarus ensured it will finish at the top of its group.

Belarus, which has never won a Billie Jean King Cup title, came to Prague without its top two players - world number two Aryna Sabalenka and two-time Australian Open champion Victoria Azarenka - and ended up losing both its group ties.

Under the tournament's new format, 12 teams have been split into four groups of round-robin play and the group winners progress to Friday's semi-finals, with the final on Saturday.

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The Russian Tennis Federation will face 18-time winners United States in the first semi-final in the morning with Australia taking on Switzerland in the evening session.

The 27-year-old Storm Sanders, who made her tournament debut this week, gave Australia the ideal start with a comfortable 6-3 6-3 win in her first meeting against an error-prone Yuliya Hatouka, ranked 192nd in the world.

"For me to come out and deliver under pressure, it's a great feeling," said Sanders, who won her singles rubber but lost the doubles against Belgium on Tuesday.

"I played a really solid match. I was a little bit tired from my two matches on Tuesday, but I came out and just fought really hard."

Aliaksandra Sasnovich jumped to a 4-0 lead in the second singles rubber against Tomljanovic before the 43rd-ranked Australian, who missed the tie against Belgium through illness, found her footing in the contest.

Tomljanovic found her mark as the match progressed and though she could not save the opening set she did enough to beat the 88th-ranked Sasnovich 4-6 6-2 6-3.

"There really is no greater feeling," said Tomljanovic. "I came here to help the team and I've ended up doing that, so that makes me happy."