Writing about the walk-out in a blog post, Martin offered his "full and complete and unequivocal" support to the strikers, despite being unable to join the picket lines in Los Angeles.

The writers of Emmy-winning drama The Handmaid's Tale have also stopped work on a new season ahead of filming that was supposed to start in late summer, co-executive producer and writer Yahlin Chang told the Reuters news agency.

The strike began last week after more than 11,000 members of the Writers Guild of America (WGA) stopped working when their contract expired, in a dispute over pay.

Late-night talk shows were the first to come off air and now A Knight Of The Seven Kingdoms, a new HBO prequel spin-off based on Game Of Thrones author Martin's The Hedge Knight novella series, is also among the major productions and ceremonies affected.

The story follows the adventures of Ser Duncan the Tall and his squire, Egg, in a period where the Iron Throne is still under Targaryen rule, before the events of the hit series.

In his blog post, Martin warned the strikes could go on for even longer than previous walk-outs in 1988 and 2007-2008, which lasted for 22 weeks and 100 days respectively.

"The writers room on A Knight Of The Seven Kingdoms: The Hedge Knight has closed for the duration," he wrote, saying that writer Ira Parker "and his incredible staff of young talents are on the picket lines".

He told his readers to "get used" to picket lines, saying: "I expect they will be there for a long time."

Recalling previous industry strikes, the author wrote: "I have been through several of these since I first started writing for television and film in 1986.

"The 1988 strike, the first I was a part of, lasted 22 weeks, the longest in Hollywood history. The 2007-2008 strike, the most recent, went for 100 days.

"This one may go longer. The issues are more important... and I have never seen the guild so united as it is now."

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Martin assured fans that the second series of House Of The Dragon, another Game Of Thrones prequel which has already begun filming, would not be affected by the strike as the scripts were finished "months ago".

Other productions affected include the final series of Stranger Things and Marvel film Blade, starring Mahershala Ali.