Katie Boulter and Charles Broom helped Great Britain beat Argentina in their Group F opener of the United Cup.

Great Britain led 1-0 after Boulter beat Nadia Podoroska 6-2 6-3 but Argentina hit back when Tomas Martin Etcheverry overcame a stomach issue to see off Billy Harris 3-6 6-3 6-2.

British number one Boulter and Broom, 26, came through their mixed doubles rubber against Maria Lourdes Carle and Etcheverry 7-6 (7-4) 7-5.

"I love playing doubles. I feel like I can relax and play my game and enjoy it even more than the singles," said 28-year-old Boulter.

"But obviously I'm very happy to get through my first singles win. It's never easy at the start of a season."

Great Britain meet Australia in their next Group F encounter on 1 January - when Boulter could face her fiancé Alex de Minaur in the mixed doubles.

Victory in the best-of-three tie would put the British side into the quarter-finals of the mixed gender team event.

Boulter admitted it would be "tough" having to play De Minaur in a deciding match.

"Let's hope we don't reach [the doubles] and we win before," she said.

Kazakhstan were the first team to secure a spot in the quarter-finals with a 3-0 win over Greece in Perth.

After Alexander Shevchenko shocked two-time Grand Slam finalist Stefanos Tsitsipas, the 2022 Wimbledon champion Elena Rybakina beat Maria Sakkari to secure top spot in Group C.

Five-time major champion Iga Swiatek - playing for the first time since it was revealed she had served a doping ban - won both her matches to help Poland beat Norway in Group B.

Poland play the Czech Republic in a tie which will decide who wins the group.

The United Cup began in 2023 with the United States winning the inaugural edition and Germany taking the title in January 2024.

British men's number two Cameron Norrie started his season with a 6-3 7-5 win against American teenager Learner Tien at the Hong Kong Open.

Norrie, 29, lost form and struggled with a forearm injury in what he described as a "challenging" 2024 campaign.

However, the former world number eight finished on a positive note by reaching the Metz final and began the new season with a solid win over 122nd-ranked Tien, who turned 19 on 2 December.

"I played a high level throughout and so did he - he's a young, up-and-coming player," said Norrie, who is 49th in the world.

"He's really calm and I was impressed with his attitude. I had to tough it out."