Novak Djokovic and Olga Danilovic of Serbia laugh on court during their mixed doubles match against Qinwen Zheng and Zhizhen Zhang of China during the United Cup tennis tournament in Perth, Australia, Dec 31, 2023. (PHOTO / AP)

PERTH - Novak Djokovic closed out his spectacular 2023 on a winning note as the world number one eased past China's Zhang Zhizhen 6-3 6-2 on his United Cup debut on Sunday before doubling up to secure a 2-1 victory for Serbia in the mixed team tournament.

The 36-year-old showed no signs of slowing down as he lifted the Australian, French and US Open trophies last season - with his only blip being a five-set defeat in the Wimbledon final - before securing the year-end top spot at the ATP Finals.

Taylor Fritz and Jessica Pegula combined to help defending champions the United States beat Britain 2-1 in Group C as they overcame Neal Skupski and Katie Boulter 1-6 7-6(4) 10-7

Djokovic wasted little time in priming himself for a tilt at a record-extending 11th trophy at the Jan 14-28 Australian Open as he dismantled world number 58 Zhang in 72 minutes at a packed RAC Arena in his first match of the 2024 season.

Zheng Qinwen rolled over Olga Danilovic 6-4 6-2 to make it 1-1 but Djokovic returned to partner Danilovic and seal a 6-4 1-6 10-6 victory against Zheng and Zhang.

Taylor Fritz and Jessica Pegula combined to help defending champions the United States beat Britain 2-1 in Group C as they overcame Neal Skupski and Katie Boulter 1-6 7-6(4) 10-7.

The Americans can book their place in the quarter-finals of the $10 million team event that features 18 countries with a win over Australia on Monday.

Boulter continued her strong start to the season after an opening win over Australia's Ajla Tomljanovic as she clawed her way back from a set and 3-0 down to quell world number five Pegula 5-7 6-4 6-4 and put Britain up 1-0.

Fritz dragged his team into contention as he managed a left thigh problem to beat Cameron Norrie 7-6(5) 6-4.

In the only match in Sydney, Canada earned a 2-1 win over Group B opponents Chile with Steven Diez and Leylah Fernandez beating Tomas Barrios Vera and Daniela Seguel 7-5 4-6 10-8.

Fernandez subdued Seguel 6-2 6-3 in the tie's opener before Nicolas Jarry won 7-5 6-4 against Diez, who had stepped in for Canadian number one Felix Auger-Aliassime.