The U.S. National Nuclear Security Administration (NNSA) could turn the existing W76 warhead into the low-yield submarine-launched weapon requested by the Donald Trump administration by dialing back its explosive yield, according to the acting head of the Department of Energy weapons agency.

“A low-yield submarine-launched ballistic missile warhead capability, deemed the W76 Mod 2, will be fielded by configuring a small number of existing ballistic missile warheads for primary-only detonation,” acting NNSA Administrator Steven Erhart said here at the ExchangeMonitor‘s annual Nuclear Deterrence Summit. Exchange Monitor is a sister publication of Defense Daily.NNSA logo

The current W76, like other thermonuclear warheads, has two explosive stages.

Erhart was cagey about whether the NNSA plans any work in the upcoming 2019 fiscal year to support W76 Mod 2 in particular, or a low-yield, submarine-launched ballsitic missile in general.

“There is no additional funding requested in 2019 for a thing called the W76 Mod 2,” Erhart said during a question-and-answer session after his prepared remarks.

The United States first fielded the W76 warhead in 1978. It is presently deployed aboard Trident II D-5 missiles carried by Ohio-class ballistic missile submarines. The Sandia National Laboratories in Albuquerque, N.M., and the nearby Los Alamos National Laboratory designed the W76, which was built by Los Alamos.

The Nuclear Posture Review released by the Pentagon in early February calls for a new low-yield submarine-launched ballistic warhead, which the Trump administration says is needed to deter Russia from using a similarly powerful nuclear weapon to escalate a military conflict fought with conventional weapons.

Moscow might feel safe using using a smaller nuke, the White House believes, because it would be more powerful than conventional forces and might not provoke a nuclear counterpunch from a country without a low-yield option.

The White House still has not released the detailed NNSA budget request for the fiscal year beginning Oct. 1 that might contain clues about any work the agency thinks it needs to start in 2019 to support W76 Mod 2, or something analogous to it.