The moment that some “Game of Thrones” fans have long feared may finally be at hand.

No, winter has not come. But the next season of the hit HBO series will be broadcast before the publication of the novel it is based on, the author said Saturday, creating a minefield of potential spoilers that may be hard for readers to escape.

The author, George R.R. Martin, said in a post on his personal blog that he had missed a Dec. 31 deadline to finish the sixth book, “The Winds of Winter,” in the best-selling fantasy series.

That “almost certainly means” the sixth season of the show — the most popular series in HBO history — will have its premiere, currently scheduled for April, before the book is published, he wrote.

“You’re disappointed, and you’re not alone,” Mr. Martin wrote to his fans in a long, frank message on his LiveJournal page. “My editors and publishers are disappointed, HBO is disappointed, my agents and foreign publishers and translators are disappointed.” He added, “But no one could possibly be more disappointed than me.”