Russia's military intervention, NATO asserted, constitutes "a breach of international law and contravenes the principles of the NATO-Russia Council and the Partnership for Peace."
"The North Atlantic Council condemns the Russian Federation’s military escalation in Crimea and expresses its grave concern regarding the authorisation by the Russian Parliament to use the armed forces of the Russian Federation on the territory of Ukraine."
NATO called upon the Russian government to "honor its international commitments... withdraw its forces to its bases, and to refrain from any interference elsewhere in Ukraine."
In its statement, NATO declared that it would support Ukraine's sovereign territorial integrity.
"Ukraine is a valued partner for NATO and a founding member of the Partnership for Peace. NATO Allies will continue to support Ukrainian sovereignty, independence, territorial integrity, and the right of the Ukrainian people to determine their own future, without outside interference."
At Ukraine's request, the NATO-Ukraine Commission convened on Sunday, with plans to engage Russia in the NATO-Russia Council.