Russia's President Vladimir Putin attends a televised meeting with regional media in St. Petersburg, Russia, April 24, 2014. Reuters/Michael Klimentyev/RIA Novosti/Kremlin

WASHINGTON -- After two decades of trying to build a partnership with Russia, the NATO alliance now feels compelled to start treating Moscow as an adversary, the second-ranking official of the North Atlantic Treaty Organization said Thursday.

"Clearly the Russians have declared NATO as an adversary, so we have to begin to view Russia no longer as a partner but as more of an adversary than a partner," said Alexander Vershbow, the deputy secretary-general of NATO.

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"In central Europe, clearly we have two different visions of what European security should be like," Vershbow, a former U.S. diplomat and former Pentagon official, said. "We still would defend the sovereignty and freedom of choice of Russia's neighbors, and Russia clearly is trying to re-impose hegemony and limit their sovereignty under the guise of a defense of the Russian world."

In April, NATO suspended all "practical civilian and military cooperation" with Russia, although Russia has maintained its diplomatic mission to NATO, which was established in 1998.

Vershbow said NATO, created 65 years ago as a bulwark against the former Soviet Union, is considering new defensive measures aimed at deterring Russia from any aggression against NATO members along its border, such as the Baltic states that were once part of the Soviet Union, Vershbow said.

"We want to be sure that we can come to the aid of these countries if there were any, even indirect, threat very quickly before any facts on the ground can be established," he said.

To do that, NATO members will have to shorten the response time of its forces, he said.

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Russia now an adversary, NATO official says