NATO has formally invited the nation of Montenegro to join the military alliance, NATO Secretary-General Jens Stoltenberg announced Wednesday.
The move is likely to displease Russia, which views NATO expansion as a threat to its security.
Montenegro started on a path to join the alliance in 2009. The formal invitation marks the beginning of accession talks, NATO says.
Montenegro already supports NATO’s efforts in Afghanistan and has actively cooperated with the alliance in other ways.
NATO expects Montenegro to make progress on reforms “especially in the area of rule of law.” During the accession talks, NATO says it will engage Montenegro in alliance activities.
Membership in NATO is voluntary and open to European democracies willing and able to contribute to Western security, the alliance says.
Aside from Montenegro, three further countries are partnering with NATO and are interested in becoming members — Georgia, Bosnia and Herzegovina, and Macedonia. The latter two were, like Montenegro, once a part of former Yugoslavia.