Russia’s top military officer warned Thursday that Moscow would strike NATO missile-defense sites in Eastern Europe before they are ready for action, if the U.S. pushes ahead with deployment.

“A decision to use destructive force pre-emptively will be taken if the situation worsens,” Russian Chief of General Staff Nikolai Makarov said at an international missile-defense conference in Moscow attended by senior U.S. and NATO officials.

Gen. Makarov made the threat amid an apparent stalemate in talks between U.S. and Russian negotiators over the missile-defense system, part of President Obama’s policy to “reset” relations with Moscow. The threat also elicited shock and derision from Western missile-defense analysts.

“It’s remarkable,” said James Ludes of the Pell Center for International Relations and Public Policy at Salve Regina University in Newport, R.I. “That Makarov would make this kind of threat in a public forum is chilling.”