U.S. military capabilities, including the American nuclear force, will “remain unmatched,” State Department spokeswoman Heather Nauert said Thursday after Russia introduced a new missile system that it said can break through current defenses.

“U.S. defense capabilities are and will remain second to none,” Nauert told reporters during Thursday’s briefing. “[W]e’re moving forward to modernize our nuclear arsenal and ensure that our capabilities remain unmatched.”