Vladimir Putin (Picture: PA).
Vladimir Putin has accused the US and the West of destabilising the Balkans with NATO expansionist policies, as Serbia prepares a hero's welcome for the Russian President.
Mr Putin arrives in Serbia on Thursday for his fourth visit to the Balkan country since 2001.
Serbia has maintained close links with Russia, even though the country formally seeks EU membership.
Belgrade has refused to join Western sanctions against Russia over Ukraine and has promised it will stay out of NATO.
Mr Putin told two Serbian pro-government newspapers that "the policy of the United States and certain Western countries aimed to foster their dominance in the region constitutes a major destabilising factor".
Despite strong Russian opposition, Montenegro joined NATO in 2017 while Macedonia is trying to settle its name dispute with Greece in order to join the Western military alliance.
Last week, NATO foreign ministers restarted a programme that could also lead to Bosnia's membership.
Serbia's four other neighbours are already members.
"In 2017, Montenegro was drawn into NATO in disregard of the opinion of half of its population," Mr Putin said.
"They did not dare to hold a relevant referendum. The country is going through a period of political instability as a result."
Two Russian military secret service operatives have been accused in Montenegro of trying to stage a coup in 2016 to stop it from joining NATO.
He said that while the West leads wrong policies in the Balkans, Russia "knows and understands the complexity of the Balkans and history of the region".
NATO's top defence chiefs discussed the Balkan country of Kosovo, and the ongoing NATO mission there, on Wednesday.
KFOR is a 28 nation peacekeeping force that involves the British Armed Forces but Britain’s presence is being reviewed after the tiny Balkan country defied Alliance calls not to form an Army.
NATO sees the move as inflaming already simmering tension between Kosovo and neighbouring Serbia.
However, chairman of NATO’s military committee, Air Chief Marshal Sir Stuart Peach, said the situation remains "unchanged" and that it is "not affected by any change in the transition of the Kosovo Security Force”.
A fountain on Belgrade's main square has been lit in the colours of the Russian and Serbian flag, ahead of Mr Putin's arrival.