WASHINGTON — Secretary of State John Kerry accused Moscow on Tuesday of accelerating the crisis in Ukraine instead of sticking to an agreement to ratchet back tensions, and said NATO partners should step up efforts to lessen Europe’s energy dependence on Russian oil.

Kerry’s comments were part of a two-punch pushback on Russia by U.S. diplomatic and military officials. At the Pentagon, a spokesman said Defense Secretary Chuck Hagel raised concerns with his Russian counterpart about “irregular military troops” under Moscow’s influence that are operating in eastern Ukraine.

Speaking at the Atlantic Council think-tank, Kerry said NATO is facing a defining moment in the strength of its alliance. He pledged anew that NATO partners — including those that border Ukraine or Russia — would be defended to the hilt if their sovereignty is threatened.

He lambasted Moscow for what he described as reneging on a diplomatic deal struck two weeks ago in Geneva to calm tensions between pro-Russian separatists in eastern Ukraine and the central government in Kiev. For weeks, separatists in eastern cities have overtaken local government buildings and stirred unrest in protesting the leadership in Kiev.

But Ukraine officials in Kiev, and much of the West, believe Russian special forces are inciting the turbulence, and fear it is a first step toward the region trying to break away from the rest of the country, as Crimea voted to do last month.