Thor has lost his hammer and the Hulk can speak in a bold new trailer for the upcoming Thor: Ragnarok shown to Comic-Con audiences.

The new film from Kiwi director Taika Waititi takes a more irreverent tone than the first two and brings the likes of Jeff Goldbum and Australia's Cate Blanchett into the fold.

Speaking on the stage at Comic-Con in San Diego Blanchett told an audience of 6,500 fans that she got involved in the franchise through a "happy accident".

"It's a universe that I've sort of been happily dragged into by my kids," she said.

Thor's alter ego Aussie star Chris Hemsworth said he became tired of the Marvel Comics superhero so he spoke to Kiwi director Taika Waititi and they agreed to give him a "mid-life crisis".

"I've put up with this character five times, this is Marvel's 167th film or something, me personally I got a bit bored myself and thought we've got to try something different," he said.

"All of us agreed, if we are going to make a third Thor we have to really push the envelope and experiment and take it to another level.

"So that was what this film was. Cut his hair, broke his hammer, changed his clothes, changed the world."

Thor will battle with Mark Ruffalo's The Hulk, who was seen to speak for the first time in a trailer that was premiered to the audience. Although, Ruffalo said he has the vocabulary of a two-year-old, Ruffalo said.

Thor: Ragnarok opens in November.