LOS ANGELES (REUTERS) - Walt Disney on Thursday (July 23) postponed the debut of its movie Mulan indefinitely, dealing a new blow to theatre operators that were counting on the live-action epic to help attract audiences during a pandemic.

Mulan was scheduled to reach theatres in March but its release has been postponed several times as many cinemas remain closed.

The film had most recently been set to debut on Aug 21 and theater operators had hoped it would help spark a late-summer rebound for movie-going.

Disney also said it had delayed the next film installments from two of its biggest franchises, Avatar and Star Wars, by one year as the novel coronavirus has disrupted production.

The Avatar sequel is now set to debut in theatres in December 2022, and the next Star Wars movie in December 2023.

"It's become clear that nothing can be set in stone when it comes to how we release films during this global health crisis,"a Disney representative said.

"Today, that means pausing our release plans for Mulan as we assess how we can most effectively bring this film to audiences around the world."

The Mulan delay follows Warner Bros decision to postpone the August release of Christopher Nolan thriller Tenet.

The two films were seen as theatres' best chance to salvage part of the lucrative summer season.

The AMC and Cineworld movie theatre chains on Thursday pushed back the reopening date for their US theatres to at least mid-August from the end of July.

The Avatar delay also removes one of next year's biggest movies.

The follow-up to James Cameron's 2009 blockbuster that is the second highest-grossing film of all time, Avatar 2 had faced numerous delays even before the coronavirus outbreak. At one time it had been expected to reach theatres in 2014.

Disney has not released details on the next Star Wars film.