MOSCOW — Russia’s military will add over 40 new intercontinental ballistic missiles this year alone that are capable of piercing any defenses, President Vladimir Putin said Tuesday in a blunt reminder of the nation’s nuclear might amid tensions with the West over Ukraine.

Putin spoke at an arms show just west of Moscow, a huge display intended to showcase Russia’s resurgent military.

NATO Secretary-General Jens Stoltenberg accused the Russians of “nuclear saber-rattling,” and said that was one of the reasons the western military alliance has been beefing up its ability to defend its members.

U.S. Secretary of State John Kerry, briefing reporters via teleconference from Boston, called Putin’s announcement concerning.

“We’re trying to move in the opposite direction,” Kerry said. “We have had enormous cooperation from the 1990s forward with respect to the structure of nuclear weapons in the former territories of the Soviet Union. And no one wants to see us step backwards.”

Russia-West relations have plunged to their lowest point since Cold War times over Moscow’s annexation of Ukraine’s Crimean Peninsula and support for a pro-Russia separatist insurgency in eastern Ukraine. The U.S. and the EU have slapped Russia with economic sanctions, and Washington and its NATO allies have pondered an array of measures in response to Russia’s moves.

The three Baltic members of the alliance, Estonia, Latvia and Lithuania, have asked NATO to permanently deploy ground troops to their nations as a deterrent against Russia. And Polish Defense Minister Tomasz Siemoniak says he and U.S. Defense Secretary Ash Carter have held talks about placing U.S. heavy army equipment in Poland.