Novak Djokovic was beaten by Alex de Minaur as Serbia lost to Australia in the United Cup quarter-finals.

World number one Djokovic received treatment to his right wrist in his 6-4 6-4 defeat by the Australian in Perth.

It was the Serb's first defeat in Australia since 2018 and comes 11 days before he begins the defence of his Australian Open title from 14 January.

Ajla Tomljanovic beat Natalija Stevanovic in the second match of the tie to secure Australia's victory.

They will meet Germany or Greece in the last four.

Djokovic needed treatment on a wrist issue during Serbia's victory over Czech Republic on Tuesday and had more treatment before world number 12 De Minaur broke serve late in the first set.

De Minaur broke again for a 4-3 lead in the second set and, despite saving three match points, Djokovic was unable to get back on terms.

Top seeds Poland reached the semi-finals with a comfortable win over China - Hurbert Hurkacz eased past Zhang Zhizhen 6-3 6-4 and women's world number one Iga Swiatek beat Zheng Qinwen 6-2 6-3.

Greece secured their quarter-final spot by beating Canada with Stefanos Tsitsipas overcoming Steven Diez 6-2 6-3 and Maria Sakkari sealing a 7-6 (7-2) 6-3 victory over Leylah Fernandez.

Caroline Garcia and Adrian Mannarino guided France into the quarter-finals by beating Italy's Jasmine Paolini and Lorenzo Sonego respectively. They will face Norway with the winner meeting Poland.