Katie Boulter admits she has “lost a lot of sleep” at the prospect of facing new fiancé Alex De Minaur on the pitch as she leads Great Britain to the United Cup quarter-finals.

Katie Boulter secured Great Britain's place in the United Cup quarter-finals with a victory over Australia's Olivia Gadecki.

After their victory over Argentina in the team competition on Monday, Great Britain knew that a straight sets win in three matches would be enough to see them top the group.

Boulter duly delivered with a dominant 6-2 6-1 victory against 97th-ranked Gadecki in Sydney.

The tie pitted the newly engaged Boulter against her fiancé Alex De Minaur, who is Australia's number one player, and she said in her on-court interview: “I'm very happy to start my new year like this.”

“I feel like I've lost a lot of sleep lately over the thought of playing against my fiancé in doubles, so I'm very tired and very happy to have passed this test.”

De Minaur later beat Billy Harris in men's singles in straight sets.

Katie Boulter admitted she “lost a lot of sleep” at the prospect of facing Alex De Minaur

The couple, who recently got engaged, faced each other in the United Cup tournament.

Boulter helped lead Great Britain to the quarterfinals after beating Olivia Gadecki in singles.

However, while Boulter will participate in mixed doubles, De Minaur will not, so the pair will not play against each other.

Instead, Boulter will play Charles Broom against Ellen Perez and Matthew Ebden, but the result will have no impact on GB's progression, where they will face Italy in the quarter-finals.

Earlier, Kazakhstan became the first team to reach the semi-finals thanks to a 2-1 victory over Germany.

World number two Alexander Zverev could be a doubt for the Australian Open after withdrawing from the qualifying round due to an arm injury.

He was replaced by Daniel Masur, who lost 6-7 (5), 6-2, 6-2 to Alexander Shevchenko after Elena Rybakina comfortably defeated Laura Siegemund, and Germany won a consolation doubles.

Iga Swiatek has had a good start to the year and again won two matches for Poland in their 2-1 victory over the Czech Republic.

The world number two beat Karolina Muchova 6-3 and 6-4 and then teamed up with Hubert Hurkacz to win 7-6 (3) and 6-3 in mixed doubles over Muchova and Tomas Machac, who they had previously beaten to Hurkacz in singles.