Sydney,  Entries from the top 16 countries and regions were announced on Thursday for the inaugural United Cup mixed team tennis event, with Greece, led by world No.3 Stefanos Tsitsipas and No.6 Maria Sakkari, as the top seeds.

Tennis Australia confirmed in a statement that world No.1 Iga Swiatek and No.11 Hubert Hurkacz will lead No. 2 seed Poland, while the third-seeded United States will feature world No.3 Jessica Pegula and No.9 Taylor Fritz.

World No.2 Rafael Nadal will team up with world No.13 Paula Badosa to fly the flag for Spain, and Italy will star world No.16 Matteo Berrettini and Martina Trevisan. France rounds out the top six seeds, with world No.4 Caroline Garcia.

Teams from Australia, Croatia, Switzerland, Germany, Brazil, Belgium, the Czech Republic, Britain, Argentina and Norway also made their way into the round-robin phase of the competition.

The top six WTA ranking-qualified countries and regions, the top five ATP ranking-qualified countries and regions, and the top five combined entry countries and regions have been admitted to the competition, reports Xinhua.

The final two remaining countries and regions (one ATP and one combined entry) will be admitted to the competition on November 21, based on the rankings published on the date, said Tennis Australia.

The group phase is scheduled to be played across Perth, Brisbane, and Sydney from December 29 to January 4. Each tie features two men's singles matches, two women's singles matches, and one mixed-doubles match.

According to the results of an official draw held on Thursday, Perth will see play-offs of Group A and Group F, with Brisbane to host Group B and Group E, and Sydney as the stage for Group C and Group D.

The United Cup, an ATP-WTA event presented in partnership with Tennis Australia, offers 15 million U.S. dollars in prize money and up to 500 ATP and 500 WTA rankings points.

Draw results:

Group A: Greece, Belgium, Qualifier ATP 6

Group B: Poland, Switzerland, Qualifier Combined 6

Group C: United States, Germany, Czech Republic

Group D: Spain, Australia, Britain

Group E: Italy, Brazil, Norway

Group F: France, Croatia, Argentina