President Joe Biden's administration has proposed building a new nuclear bomb as the production of weapons to replace the aging U.S. stockpile ramps up.

The Department of Defense (DoD) announced on Friday that it was pursuing the development of a new variant of the B61 gravity bomb, a type of weapon that was first produced in the 1960s, at the height of the Cold War. Until very recently, U.S. nuclear weapons production had largely been at a standstill since the Cold War ended with the dissolution of the Soviet Union in 1991.

Weapons in the B61 series, a key part of the existing U.S. stockpile, are so-called "tactical" gravity bombs, unguided weapons designed to detonate at targets reached after being dropped out of an airplane. The DoD said in a press release that the new variant, the B61-13, was needed "to assure our ability to achieve deterrence and other objectives."

"The B61-13 will strengthen deterrence of adversaries and assurance of allies and partners by providing the President with additional options against certain harder and large-area military targets," the release states, while adding that the bomb would "include the modern safety, security, and accuracy features" of the B61-12, an Obama-era variant.