LONDON (AFP) - Serena Williams postponed her Wimbledon media duties for a royal appointment on Saturday (June 30) as the American star joined the Duchess of Sussex at a polo match.

Williams is a close friend of Meghan Markle and the seven-time Wimbledon champion was a guest at her wedding to Prince Harry at Windsor Castle in May.

Journalists at Wimbledon were expecting Serena to discuss her first appearance at the Grand Slam since becoming a mother for the first time last September.

But instead the 23-time major winner put her scheduled press conference on hold after a morning practice session with her sister Venus at the All England Club.

Wimbledon officials announced the postponement only minutes before Williams was due in the media room.

Just hours later, Serena and her husband Alexis Ohanian were photographed arriving for the Audi Polo Challenge in Ascot, where Prince Harry and his brother Prince William were among the players.

Williams will be back at Wimbledon for a press conference on Sunday morning, with defending champions Garbine Muguruza and Roger Federer also due to conduct their pre-tournament interviews.

Wimbledon gets underway on Monday, with 25th seed Williams scheduled to play Holland's Arantxa Rus in the first round.