The fifth World Baseball Classic, scheduled to be held in March of 2021, is now under threat from the coronavirus pandemic, Nippon Professional Baseball's secretary general Atsushi Ihara said Thursday.

The tournament, organized jointly by Major League Baseball and its players union, has been held in March since the first tournament in 2006, won by Japan, which also won the 2009 tourney. NPB has never been a fan of the March time frame, and with the pandemic still raging and the Tokyo Olympics now postponed until 2021, a March window would throw Japan's participation in doubt.

"Thinking of our schedule next year, there are things I want to talk about soon and get together with the organizers," Ihara said.

Next year's tournament, originally scheduled for March 9 to March 23, is set to expand from 16 teams to 20, but qualifiers that were to be played in Arizona last month have been postponed.

NPB's 2020 season was due to start a week earlier in order to have a three-week Olympic break, but that break will be hard to replicate for the Olympics next year if the WBC takes place in March.

NPB and its players union threatened a boycott of the first two WBCs, in 2006 and 2009, over the March timing. Ahead of the 2013 tournament, the union balked over distribution of sponsorship revenue, much of which comes from Japanese companies.

Although Japan has failed to reach the last two finals, the loss of sponsorship revenue should Japan sit out would be a huge blow to the tournament.

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