Officials belonging to the North Atlantic Treaty Organization (NATO) said on Monday the smallest country in the former Yugoslavia would likely be invited to join the military alliance at this week's meeting. It's a move expected to heighten tensions between Russia and NATO's member states, which include the US, UK, Turkey and Germany.

NATO foreign ministers will formally make the decision once all member nations gather in the Belgian capital, where they'll discuss issues including Syria and the ongoing conflict in the Ukraine.

While no decision has been made yet, NATO sources said it was likely Montenegro would be approved as the 29th member. It will join other Balkan countries, including Croatia and Albania, who have joined the military alliance over the past several years.

Tension in the East

NATO offered Ukraine a chance to join in 2008 following Russia's war with Georgia, but Kyiv decided against it. Recently, however, Ukrainian President Petro Poroshenko has expressed interest in joining the military bloc.

In an interview with Interfax news agency last week, Russian Foreign Ministry official Andrej Kelin said Montenegro's acceptance into the bloc would be a significant blow to NATO's relations with Moscow.

Most of the former Soviet states of the Cold War-era Warsaw Pact have joined NATO.

blc/gsw (dpa, AFP)