House Democrats on Thursday introduced a bill to ban the low-yield, submarine-launched ballistic-missile warhead the National Nuclear Security Administration recently acknowledged it has begun producing.

Rep. Ted Lieu (D-Calif.) leads the cadre of Democrats, which includes House Armed Services Committee Chairman Adam Smith (D-Wash.). The text of the bill, “H.R.1086 – To prohibit the research and development, production, and deployment of the Trident D5 low-yield nuclear warhead, and for other purposes,” was not available at deadline Friday.

All 21 of the bill’s co-sponsors are Democrats. Smith, who unconditionally opposes the low-yield warhead and has said so since Congress approved and funded it last year, could include the text of Lieu’s bill in the 2020 National Defense Authorization Act: an annual policy bill that sets spending limits for defense programs including those of the National Nuclear Security Administration (NNSA).

The bill just unveiled made its first appearance in the 115th Congress, which ended Jan. 3, along with the Democrats’ minority in the House. The warhead would tip Trident II-D5 missiles made by Lockheed Martin [LMT], which are carried aboard the Navy’s Ohio-class submarines.

Republicans, who last year supported and funded the W76-2 low-yield warhead, still control the Senate. The Trump administration ordered the NNSA to build the low-yield warhead in the 2018 Nuclear Posture Review. The administration says the U.S. needs the weapon to check similarly powerful Russian weapons that some fear Moscow would use to win a war it starts, but cannot finish, with conventional weapons.

Smith and other Democrats on Capitol Hill — including some running for president in 2020, including Sens. Kirsten Gillibrand (D-N.Y.), Kamala Harris (D-Calif.) and Elizabeth Warren (D-Mass.) — argue that any use of nuclear weapons would escalate into a full-scale, civilization-ending nuclear war.

The NNSA, as first reported by Defense Daily affiliate publication Nuclear Security & Deterrence Monitor, has said it will deliver the first W76-2 warheads to the Navy by October. It is not clear when the agency started manufacturing the weapon, which is a modified version of the existing W76 submarine-launched ballistic-missile warhead the agency finished refurbishing in December.

In a report posted online this week, the independent federal Defense Nuclear Facilities Safety Board said the NNSA in January “initiated operations on a new weapons modification,” the operations of which “are nearly identical to previously authorized operations” at Pantex. A spokesperson for the Defense Nuclear Facilities Safety Board did not reply to a request for comment this week.

Sen. Dianne Feinstein (D-Calif.) last year said the low-yield W76-2 would cost about $125 million in fiscal years 2019 and 2020. The program has a $65 million budget in 2019. That is a fraction of the cost of the decades-long, $4-billion W76-1 life extension program NNSA completed in December.