The US is updating its nuclear arsenal amid growing security fears

The Department of Defense announced Saturday the US plans to add a new model of nuclear bomb to its arsenal.

The new gravity bomb will be called B61-13, a variant on the existing B61 model that was first introduced in the 1960s. The Department of Energy's National Nuclear Security Administration will begin production pending Congressional authorization and appropriation, according to a Department of Defense statement.

The previous model, B61-12, can carry out earth-penetrating attacks, low-yield and high-yield attacks, above surface detonation, and bunker-buster options, Insider previously reported.

The move is the result of a "changing security environment" and not any specific event, according to a fact sheet provided by the department.