Joss Whedon says new 'Avengers' villain Ultron will ''juice things up''.

The director recently revealed the highly anticipated sequel to his 2012 superhero team-up movie will be called 'The Avengers: Age of Ultron', and he believes the robotic comic book villain will be a formidable foe for Robert Downey Jr.'s Iron Man and friends.

He told Total Film magazine: ''I was pitching Ultron before I took the job on the first movie. I was like, 'I don't know if I want to do this, but for the second one, you should totally do Ultron.' Because he's been a thorn in their side as much as any other character over the years and particularly back in my history.

''He was great. He's somebody who can juice things up and he's a real problem for the Avengers. That's not always easy to find. It's not like the Vulture is really going to give them a hard time for 20 minutes.''

All of the core 'Avengers' cast are set to return for the 2015 follow-up film including Downey, Chris Hemsworth, Chris Evans, Mark Ruffalo, Samuel L. Jackson, Scarlett Johansson and Jeremy Renner.

Meanwhile, 'Kick-Ass 2' actor Aaron Taylor-Johnson has confirmed he is in talks to play a new addition to the movie, speedy superhero Quicksilver.

'The Avengers: Age of Ultron' opens in the UK on May 1, 2015.