Brad Pitt: 'Heart of the Beast is the hardest movie I've ever made'

Brad Pitt has described Heart of the Beast as the "hardest movie" he's ever made.

In a new interview with Collider, the 62-year-old star discussed the physical demands involved in shooting the new survival thriller directed by David Ayers.

Pitt plays a former Special Forces soldier who becomes stranded alongside his combat dog in the Alaskan wilderness, following a harrowing plane crash.

"Physically, I would absolutely say this is the hardest movie I've ever made, but also very rewarding," he revealed.

When asked to elaborate on the challenges, Pitt singled out the "extreme conditions" as one of the toughest obstacles he had to overcome.

However, he insisted his battle with the great outdoors make the film more realistic.

"It's not like we could go back to the trailer and dry off or anything," he explained.

"You get in in the morning, you get wet, and you stay wet all day until the end of the day. There is a drudgery involved in that, but at the same time, I've got to say, I believe in it because it informs the scene, it informs the characters, and it informs our movie in the end."

Elsewhere in the interview, Pitt revealed he agreed to star in the film after Ayer sent him the script - and he was left deeply touched by the "love story" ending.

The star recalled having tears in his eyes as he read the final pages.

He also felt compelled to star in his own survival movie after being inspired by movies including The Revenant.

"I've always loved a survival movie and always wanted to do one since... Jeremiah Johnson is one of my favourites, and Leo DiCaprio did such a beautiful one," he mused.

Heart of the Beast is released in cinemas from 25 September.