Nick Kyrgios has withdrawn from the United Cup on the eve of the inaugural edition of the tournament, with Australia team captain Samantha Stosur admitting "it's news to all of us."

The 2022 Wimbledon finalist, who has been struggling with an ankle injury, was due to line up alongside the likes of Alex De Minaur and Ajla Tomljanovic in the new team event.

However, Kyrgios surprised team-mates with his decision to pull out of the event, in which Australia face Great Britain in their opening match on Thursday, reportedly switching his focus to achieving full fitness for next month's Australian Open.

"I'm not going to speak for Nick’s summer, we've got to leave that for him," Stosur said at a press conference. "He was here. We literally just found out 10 minutes ago, so it's obviously news to all of us.

"But we just move forward now. We're all happy to be here and keen to get out there. Now that's out there, and we move forward with the placings of the team and do our best on the day.

"As far as the men's side of this team goes, we're in very capable hands still, so I'm not concerned that our chances have just diminished greatly or anything like that. We're out here to do everything we can possible to try and win this competition."

De Minaur added: "We've all just heard. Ultimately, we're just going to get ready. We’ve got a great team, and we're all going to be out there doing our best. So ultimately, the only thing that changes is match-ups and that's about it."