George RR Martin has thanked his fans for the “astonishing … outpouring of support”, which followed his admission on Saturday that he would not be able to finish his novel The Winds of Winter before the new TV series of Game of Thrones airs this spring.

Martin revealed on his website on 2 January that, although he had been given an extended deadline of the end of 2015 to complete the long-awaited novel – the sixth in his fantasy series A Song of Ice and Fire – he had not been able to meet it, meaning the source material will come out after the TV adaptation is broadcast.

“Yes, there’s a lot written. Hundreds of pages. Dozens of chapters,” he wrote. “But there’s also a lot still left to write. I am months away still … and that’s if the writing goes well.”

Martin and his publishers had wanted The Winds of Winter to be published before the sixth series of the hit HBO television series airs, but this will now not be possible, he told fans, adding that “there are no excuses. No one else is to blame ... It’s on me. I tried, and I am still trying.”

The fantasy author has been criticised by fans in the past over the speed of his writing; in 2009, it reached such levels that Neil Gaiman was moved to pledge his support, telling a demanding reader that “George RR Martin is not your bitch”.

This time, though, Martin’s readers were quick to encourage him, with the more than 1,000 comments on his blog ranging from “Love your work, George! Get it done when it’s done. I’ll be there” to “Don’t sweat it, George” and “Take as long as you need to, sir”.

“That couldn’t have been fun to write,” wrote one reader in response to Martin’s blog. “But fact is in 50 years readers will judge on the book’s quality and not if they met some arbitrary deadline and beat the TV adaptation. As much as I’d like to see it released soon, I ultimately approve of the priority on quality.”

Martin later responded to his fans, saying that “the outpouring of support in response to my post on The Winds of Winter has been astonishing”.

“Thank you all, so very much. There were 40 pages of screened comments on the post by the time I logged on this morning. I haven’t even been able to read half of them as yet,” he wrote. “I cannot tell you how much I appreciate all the kind words and good wishes.”

The fifth novel in Martin’s A Song of Ice and Fire series, A Dance With Dragons, was published in 2011, shortly after the first season of the HBO series Game of Thrones began to air.

Addressing fans concerned that the new TV series, which airs in April, might “spoil” the books, Martin admitted that “given where we are, inevitably, there will be certain plot twists and reveals in season six of Game of Thrones that have not yet happened in the books”, but added that “some of the ‘spoilers’ you may encounter in season six may not be spoilers at all … because the show and the books have diverged, and will continue to do so”.

Some characters, he said, are dead in the show and alive in the books, while others have never been part of the show and are major players in the books.

“Game of Thrones is the most popular television series in the world right now,” wrote Martin. “It’s an incredible production with an incredible cast and crew. The Winds of Winter should be pretty good too, when it comes out. As good as I can make it, anyway ... Enjoy the show. Enjoy the books. Meanwhile, I’ll keep writing. Chapter at a time. Page at a time. Word at a time. That’s all I know how to do.”