The NATO military alliance honored its newest member by raising Montenegro’s flag at its headquarters in Brussels on Wednesday, at a time Russia has warned of consequences as NATO expands eastward.

Montenegro is now the 29th member of the military alliance, and the country's President Filip Vujanovic has promised that the move will come with huge benefits for his people –however, not everyone seems to agree with the newest addition.

Russian President Vladimir Putin has said that a bigger and stronger NATO is simply a tool of US foreign policy to keep Moscow in check, CGTNs’ Kevin Ozebek reported.

Moscow has expressed its anger and noted it is ready to strike back, if need be.

A statement released from the Russian foreign ministry indicated that Moscow has now the right to retaliate against the small Balkan nation for joining NATO and noted that for every political action there is an equal reaction.

Meanwhile, NATO generals said expanding and stationing troops close to Russia’s borders is a necessary step to reassure eastern European allies worried about possible Russian aggression.

But NATO's arguments are challenged by security experts who have noted that one problem facing the alliance is Europe's division in opinion over how much of a threat Russia really poses.