By Hanna Rantala

LONDON, March 20 (Reuters) - Creators of the long-running hit series "Game of Thrones", David Benioff and D.B. Weiss, return to television with another ambitious project; science-fiction show "3 Body Problem".

The duo has joined forces with "True Blood" writer-producer Alexander Woo to bring Chinese author Liu Cixin's bestselling novel "The Three-Body Problem", the first book of a trilogy, to the screen in the new Netflix series.

"It's probably even more ambitious than 'Game of Thrones'," said John Bradley, who played Samwell Tarly in the HBO show and now stars as scientist-entrepreneur Jack Rooney.

"With this, we flash back in time, we're in the present, we're in a virtual reality video game, which means we can show anything. We were only limited by our own imaginations, really, and that kind of scope, it's a gift," he said at the show's London premiere on Wednesday.

"3 Body Problem" opens in Beijing in 1966 during the Cultural Revolution and takes audiences across time and the globe - and further. Partly set in a virtual reality game, it sees actions taken by an astrophysics student in China carry consequences on the entire universe.

In present-day Britain, a group of physicists, nicknamed "The Oxford Five" seek to understand why scientific experiments around the world are failing. They get a helping hand from unconventional detective, Da Shi (Benedict Wong), an operative of a secret intelligence agency.

The eight-episode series' ensemble cast includes actors Eiza Gonzalez, Jovan Adepo, Jess Hong and Jonathan Pryce, while Brad Pitt, Rosamund Pike and Rian Johnson are among the show's executive producers.

"This is a story that involves science and fiction, but it's not like crazy aliens on a crazy planet coming in with costumes. It's, essentially, a kind of genuine threat that humanity faces and it's how we all deal with that threat," said Pryce.

As for adapting the other two books in the trilogy, Liam Cunningham, another "Game of Thrones" alumn who plays Thomas Wade, said the show's creators were keeping mum on their plans.

"I've heard a couple of rumours," he said.

"I like the surprises of it and I used to love it with 'Game of Thrones' as well. You didn't even know when you're going to die until you got the script. It's a little unpredictable and it keeps the interest up."

"3 Body Problem" starts streaming on Netflix on March 21. (Reporting by Hanna Rantala; Editing by Stephen Coates)