Lucas Till will star in 'X-Men: Days of Future Past.'

Director Bryan Singer has confirmed the 'X-Men: First Class' actor will be rejoining the mutant franchise, reprising his role as Alex Summers, aka Havok.

Singer posted a suggestive picture of Till in army uniform in a military base via Twitter on Monday (15.07.13).

He captioned the photo: '''Mankind must put an end to war before war puts an end to mankind.' -JFK @lucastill #xmen #DaysOfFuturePast (sic)''

Till joins Jennifer Lawrence, Michael Fassbender, James McAvoy and Nicholas Hoult as the only actors to return from the the 2011 'X-Men' prequel film.

The cast will also include stars from the original 'X-Men' trilogy - which ran between 2000 and 2006 - including Sir Ian McKellen, Sir Patrick Stewart, Hugh Jackman and Halle Berry.

The news of Till's casting comes after it was revealed movie studio 20th Century Fox will send a dozen cast members to San Diego Comic-Con this weekend for surprise announcements about the upcoming film.

It was recently confirmed that Peter Dinklage will play a character named Bolivar Trask, and Josh Helman will play a younger version of William Stryker.

Helman will be the third actor to play the character in the franchise, following in the footsteps Brian Cox and Danny Huston.

Cox played the character in the present day in 2003's 'X2', while Danny Huston played the character circa 1981 in 2009's 'X-Men Origins: Wolverine'.