Vietnamese was preparing to hold its first international boxing tournament featuring eight fights, including between its first woman Asia Pacific boxing champion, Nhi, and Etsuko Tada in Quang Ngai Province on February 27.
But the Japan Boxing Commission (JBC) did not grant permission for its boxers to fight abroad amid the pandemic.
The JBC and HCMC-based boxing gym Cocky Buffalo, one of the Vietnamese organizers, agreed to postpone the event.
The WBO announcement did not mention the exact date.
Nhi defeated Kanyarat Yoohanngoh of Thailand in 10 rounds to take the WBO Asia Pacific minimumweight crown in Cambodia early last year.
Vietnam has great hopes the 24-year-old could become the first to bring home the world title from the bout with Tada.
Tada won the vacant WBO 105-pound belt last December in Japan.