Nicola Adams has postponed her 8 March fight against Mexican Arely Mucino - the Briton's first shot at a world title - because of injury.
The two-time Olympic champion, 36, was due to challenge for the WBO flyweight title at London's Royal Albert Hall.
But a statement from promoter Frank Warren said Adams had "picked up an injury during her preparations".
"The world title bout will now be rescheduled to take place later in the year," the statement added.
Undefeated British light-heavyweight Anthony Yarde will now face Travis Reeves of the United States as the main event.
A bout with Mucino would have been Adams' sixth since turning professional in 2017 and she said in January she wanted to win her first title to emulate her "hero" Muhammad Ali, who boxed at the Royal Albert Hall in 1971 and 1979 exhibitions.
The contest was also set to take place on International Women's Day.
Adams earned a unanimous points victory to defeat Isabel Millan of Mexico in her previous fight in October.
Mucino, 29, claimed her world title in February 2018 and has a record of 27 wins, two draws and three losses in 10 years as a professional.