Defense Secretary James Mattis James Norman MattisBiden courts veterans amid fallout from Trump military controversies Trump says he wanted to take out Syria's Assad but Mattis opposed it Gary Cohn: 'I haven't made up my mind' on vote for president in November MORE on Tuesday defended the Trump administration’s nuclear weapons policy against charges it sidelines arms control and lowers the threshold for using the weapons.

“I recently received a letter from senators concerned that the 2018 Nuclear Posture Review would ‘undermine decades of U.S. leadership on efforts to reduce and eventually eliminate the existential threat posed by nuclear weapons,’ ” Mattis told the House Armed Services Committee.

“To the contrary, the 2018 Nuclear Posture Review reaffirms the mutually reinforcing role of nuclear deterrence in a complex and dynamic security environment while underscoring continued U.S. commitment to nonproliferation, counter-nuclear terrorism and arms control.”

Mattis’s testimony was his first public remarks on the Nuclear Posture Review since the Pentagon released it Friday afternoon.

ADVERTISEMENT

In response to what the report describes as Russia’s growing nuclear power, the review calls for two new U.S. capabilities: a sea-launched nuclear cruise missile and a so-called low-yield warhead for submarine-launched ballistic missiles.

Arms control groups and Democratic lawmakers have expressed alarm at the plans, saying they are overly costly, could spark a new nuclear arms race and could lead to a greater willingness to use nuclear weapons if officials believe “low-yield” is less destructive.

Pressed by lawmakers Tuesday about the planned sea-launched cruise missile, Mattis said it was meant to provide leverage over Russia while diplomats work to get Moscow back into compliance with an arms treaty.

The United States has accused Russia of violating the Intermediate-range Nuclear Forces (INF) Treaty by deploying a banned cruise missile. The landmark 1987 accord bans ground-launched ballistic and cruise missiles with ranges between 500 and 5,500 kilometers.

"I don't think the Russians would be willing to give up something to gain nothing from us," Mattis said, suggesting the cruise missile will be used a bargaining chip.

Pressed further by Rep. Rick Larsen Richard (Rick) Ray LarsenDemocratic lawmaker calls for stronger focus on trade leverage to raise standards The Hill's Morning Report - Presented by Facebook - Biden, Harris launch Trump offensive in first joint appearance The Hill's 12:30 Report: Biden, Harris's first day as running mates MORE (D-Wash.) on whether the U.S. would abandon the missile if Russia returns to compliance, Mattis said he didn’t “want to say in advance of a negotiation."

Mattis also pushed back on the idea that having low-yield weapons lowers the threshold for using nuclear weapons.

“What it does is it makes very clear that we have a deterrent if the Russians choose to carry out what some their doctrine leaders have promoted, their political leaders have promoted, which would be to employ a low-yield nuclear weapon in a conventional fight,” Mattis said. “We want to make certain they recognize that we can respond in kind. We don’t have to go with a high-yield weapon, thus the deterrent effort stays primary. It is not to in any way lower the threshold to use nuclear weapons.”

He also said he does not believe there is such a thing as a “tactical” nuclear weapon.

“Any nuclear weapon used any time is a strategic game-changer,” Mattis continued. “That said, we don’t want someone else to miscalculate and think because they’re going to use a low-yield weapon that somehow we would confront what Dr. [Henry] Kissinger calls surrender or suicide. We do not want even an inch of daylight in how we look at the nuclear deterrent. It is a nuclear deterrent and must be considered credible.”