SYDNEY (AP) Roger Federer has pulled out of the inaugural ATP Cup.

Organizers wrote on Twitter that Federer withdrew ''due to family reasons and therefore Switzerland has been withdrawn as a country that qualified at the first entry deadline.''

The ATP Cup will open the 2020 season in Australia from Jan. 3-12, with two four-team groups in each of Brisbane, Perth and Sydney. The Swiss were drawn into a group with Belgium, Britain and one other nation.

Eight teams from the six-day group stage advance to the knockout rounds in Sydney.

The ATP Cup joins a crowded 2020 season. It includes two other team events - the Davis Cup and Laver Cup, which the 38-year-old Federer part-owns - and the Tokyo Olympics.