WASHINGTON — The Trump administration is poised to get congressional authorization to start building a controversial new submarine-launched low-yield nuclear weapon.

The Senate and House came together Monday on a $716 billion defense authorization report that authorizes $65 million to develop the weapon, aimed at deterring Russia, according to the bicameral compromise conference report.

The requirement for the weapon — likely to be a submarine-launched Trident II D5 with a W76-2 warhead — is part of the administration’s Nuclear Posture Review.

The report for the sweeping 2019 National Defense Authorization Act is expected to come to a vote in the House this week and the Senate next week. The annual must-pass bill covers military hardware, personnel and a wide swath of hot-button national security issues.

In a minor win for opponents of the new weapon, the energy secretary would not be able to reprogram money to begin a nuclear weapons program or begin a new phase of a nuclear weapons program.

Low-yield nuclear weapons per 2004 law need special authorization from Congress, but the new legislation would make them equivalent to other nuclear weapons, with the same authorization requirements. That’s a win for W76-2 advocates.

It’s the latest move in a mostly partisan battle that saw the Senate Appropriations Committee approve a Pentagon spending bill with language to order more study before the weapon can be developed. The fate of the larger bill was unclear as of Tuesday.

Congressional Republicans and the Pentagon are advocating for the systems to deter Russia from using its own arsenal of low-yield nuclear weapons. Still, many Democrats and nonproliferation advocates see it as lowering the threshold for a nuclear war.

More broadly, the compromise conference report includes a sense of Congress that expresses support for the administration’s Nuclear Posture Review — and meets the president’s budget with $142.2 million for the National Nuclear Security Administration’s nuclear weapons activities and defense nuclear nonproliferation program, according to a House Republican summary.

The bill would also increase authorized funding to accelerate two key Air Force nuclear modernization programs: the Ground Based Strategic Deterrent and the Long Range Standoff cruise missile.

Note: An earlier version of this story partially misstated the legislation’s impact on congressional oversight of a low-yield nuclear weapon.

Joe Gould was the senior Pentagon reporter for Defense News, covering the intersection of national security policy, politics and the defense industry. He had previously served as Congress reporter.

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