UNSC, EU, NATO to hold urgent meetings over Ukraine
Saturday, March 01, 2014
Meanwhile, Lithuania and Latvia called upon the North Atlantic Council, the decision-making body of NATO, to hold an extraordinary session on Ukraine, citing security concerns.
Specifically, they have invoked Article 4, which states
Article 4
The Parties will consult together whenever, in the opinion of any of them, the territorial integrity, political independence or security of any of the Parties is threatened.
Since, as has been noted, Ukraine is not a member of NATO, then Latvia & Lithuania seem to be referring to themselves as "the territorial integrity, political independence or security of any of the Parties is threatened".