The National Nuclear Security Administration (NNSA) in January completed its first low-yield, submarine-launched, ballistic-missile warhead, which now awaits a final design review in Texas before the agency can ship it off to the Navy, an agency official said Tuesday.

NNSA finished building the first low-yield W76-2 warhead, a modified version of the recently refurbished W76-1, at the Pantex Plant in Amarillo, Texas late last month, John Evans, acting assistant deputy administrator for stockpile management for the NNSA, said in a question-and-answer session at the ExchangeMonitor’s annual Nuclear Deterrence Summit in Arlington, Va.

The weapon now requires a final review before NNSA can declare it an official “first production unit.” After that review, slated for February, the agency can begin preparations to send the weapon to the Navy. Like the much higher-yield W76-1, the W72-2 will fit on a Trident II-D5 missile carried aboard an Ohio-class ballistic missile submarine.

In January, when it acknowledged it had started building the first W76-2, NNSA said it would start delivering the weapon to the Navy by Sept. 30. NNSA has not said exactly how many W76-1s it will convert into W76-2’s, only that it is a “small number.”

The Trump administration called for a low-yield, submarine-launched ballistic-missile warhead in February 2018 as part of the latest U.S. Nuclear Posture Review. The administration claims the U.S. needs the weapon to dissuade Russia from using a similarly powerful nuclear weapon to win a war it starts, but cannot finish, with conventional weapons.

Opponents of the low-yield warhead, including new House Armed Services Committee Chair Rep. Adam Smith (D-Wash.), say the weapon should be banned because any nuclear attack — including a low-yield one — will inevitably escalate into an arsenal-emptying, civilization-ending, nuclear exchange. Smith is a co-sponsor on an all-Democrat bill to ban the low-yield warhead.

Evans said that the Department of the Defense requires NNSA to finish work on the W76-2 warhead in fiscal year 2024.

“The military requirement is for us to complete by 2024,” Evans said from the stage in response to an audience question. If “we complete early, so much the better. We will not be late. Once we start, we’re going to ramp up activities and complete as soon as we can.”

NNSA last year thought it would need another $60 million for the W76-2 in fiscal year 2020, Sen. Dianne Feinstein (D-Calif.) said in an open appropriations markup in April 2018. Congress approved $65 million for the weapon in fiscal year 2019, as the White House requested.

The 2018 Nuclear Posture Review that hatched the W76-2 also called for researching a nuclear-tipped sea-launched cruise missile. NNSA plans to request funding for that study in its fiscal year 2020 budget, according to the 2019 Stockpile Stewardship and Management Plan the agency released late last year.

The Trump administration plans to release at least an outline of its 2020 budget request in March, Defense Daily has reported.